1/30/2011
A hacker managed to obtain evidence of data manipulation on global warming !!!

Something extraordinary happens in the world debate on global warming. On Thursday, November 19, 2009, announced that a hacker has managed to get 160 megabytes of data and collection of mail from the server Climate Research Unit (CRU) at the University of East Anglia (UAE) in the UK. Emails that contained conversations between the principal investigator at the site since 1997 until now, and apparently, email it shows the manipulation of data on global warming.


Very interesting. Previously we had a hacker named Gary McKinnon who break into computer networks owned by NASA, the Department of Defense and the U.S. military only to find classified information about ufo. Now we have the Anonymous hacker who jumped directly into the global warming debate by breaking into computer networks research organization in the world's leading global warming.
As we know, the progress of science depends on complete and accurate data, not even the science of global warming. But in recent days, the world was shocked by the disclosure of inconsequential practices conducted by researchers of global warming, of course I mean the researchers pro-Al Gore.
Andrew Bolt, a writer even said that this scandal could be the biggest scandal in the history of modern science.
Not long ago we offered frightening news that the polar ice will melt within 20 years total. Then not long after that, the IPCC (the UN agency on climate change) through its chairman, Dr RK Pachauri released a statement that the ice in the Himalayas will melt the total in 2035. Even according to him, the melting ice could be more quickly if "we do not do something."
It seems ahead of climate conference in Copenhagen to be held in December, the scientists became more pro-Al Gore often said the "prediction" about the equivalent masiv disaster movie "2012" you just watch. In other words, these scientists have created a "doomsday prophecy 2012" new.
Meanwhile, scientists in other parts of the world, which usually have limited the technology, can only receive raw data from the western world. Yes, maybe many of us who do not know that climate change data that we know (and reported by the media) was not derived from the research that we do own. Most of the data comes from a place called the Climate Research Unit (CRU) at the University of East Anglia (UAE), UK. The organization also supplies the data for the IPCC and researchers pro Al Gore other.
Well, in a heated debate between scientists pros and cons of Al Gore is a hacker has finally decided to get into the arena. CRU emails from the burglarized was published on the internet by a hacker who calls himself "FOIA."
In the email, the researchers who have discovered the same ideology agreed to cover up global warming data that does not comply with their claims. Email this has been confirmed to the CRU and they acknowledge that the contents of emails that appeared in the media have descended from their servers.
One of the emails that have been successfully obtained from a conversation between Prof. Phil Jones, head of the CRU and Prof. Michael E Mann of Pennsylvania State University. These two men are the main supporters of Al Gore in a matter of global warming.
In one conversation, Prof. Jones suggested to Prof. Mann to do the "trick" to change the climate data in each series to hide the decline in global temperatures.
"I've been using the trick from Mike to add new data on the actual data from each series in the last 20 years and from 1961 to hide the decline (temperature)."
After the scandal was uncovered, Prof Mann explained to the New York Times that scientists commonly use the word "trick" to refer to how best solve a problem and does not mean something secret (???).
In another email, Prof Jones also said that he would rather erase the data that are inconsistent with their claim instead of sending the data to other researchers. Prof Jones also encourage Prof Mann to do the same.
In the year 2009, CRU get a lot of criticism for refusing to release the data used to create the Earth's surface temperature history report. Demand from researchers and other scientists have been rejected and in some cases, making the report acknowledges that the original data used is gone.
Email the above seems to confirm everything.
In addition to conversations that occur between these two professors, who had burglarized another email is the email that comes from Tim Osborn, one of the other professors in the CRU. In his email, Prof. Osborn discuss with colleagues about how to cut the data to hide the downward trend in global climate temperature.
Then in another email, Prof. Osborn Professor Mann asked not to forward the data it sends to others because the data that the researchers confirmed the theory of global warming, anti-Al Gore.
Not only that, one of the emails also contained comments about the death of John L. Daly, a researcher opponent Al Gore. The comment reads, "In a strange way, actually this news is good news."
Given these recent developments, Senator James Inhofe's famous anti-global warming Al Gore's version also has demanded the U.S. Congress to investigate the Pennsylvania State University and several other universities are known to be involved in the falsification of this data.
Earlier, shortly after the predictions of melting ice in the Himalayas was released by the IPCC, the Indian government through the ministry of the environment has released a statement which wants an independent study of the condition of snow in the Himalayas. The data used in the current Indian government is the data derived from western researchers.
Given the large number of emails successfully broken, then the email content is checked further by other researchers to find evidence of other lies. If found evidence of high-level conspiracy, then the case is of course really will be the biggest scientific scandal in the world.
Is Himalayan snow will melt the total in 2035? The answers to these questions will greatly depend on the objectivity of the research on Himalayan snow.
Those who are not knowledgeable will be very easily deceived. So the question is when can we have the knowledge and world-caliber technology so that we can decide for ourselves whether the world is warming or cooling.


from : http://xfile-enigma.blogspot.com/2009/11/seorang-hacker-berhasil-mendapatkan.html
1/18/2011
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1/11/2011
  HTML definition











HTML, which stands for HyperText Markup Language, is the predominant markup language for web pages. HTML is the basic building-blocks of webpages. A markup language is a set of markup tags, and HTML uses markup tags to describe web pages.
HTML is written in the form of HTML elements consisting of tags, enclosed in angle brackets (like <html>), within the web page content. HTML tags normally come in pairs like <h1> and </h1>. The first tag in a pair is the start tag, the second tag is the end tag (they are also called opening tags and closing tags).
The purpose of a web browser is to read HTML documents and compose them into visual or audible web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page.
HTML elements form the building blocks of all websites. HTML allows images and objects to be embedded and can be used to create interactive forms. It provides a means to create structured documents by denoting structural semantics for text such as headings, paragraphs, lists, links, quotes and other items. It can embed scripts in languages such as JavaScript which affect the behavior of HTML webpages.
Web browsers can also refer to Cascading Style Sheets (CSS) to define the appearance and layout of text and other material. The W3C, maintainer of both the HTML and the CSS standards, encourages the use of CSS over explicitly presentational HTML markup.


In 1980, physicist Tim Berners-Lee, who was a contractor at CERN, proposed and prototyped ENQUIRE, a system for CERN researchers to use and share documents. In 1989, Berners-Lee wrote a memo proposing an Internet-based hypertext system.Berners-Lee specified HTML and wrote the browser and server software in the last part of 1990. In that year, Berners-Lee and CERN data systems engineer Robert Cailliau collaborated on a joint request for funding, but the project was not formally adopted by CERN. In his personal notes from 1990 he lists"some of the many areas in which hypertext is used" and puts an encyclopedia first.

 The first publicly available description of HTML was a document called HTML Tags, first mentioned on the Internet by Berners-Lee in late 1991.It describes 20 elements comprising the initial, relatively simple design of HTML. Except for the hyperlink tag, these were strongly influenced by SGMLguid, an in-house SGML based documentation format at CERN. Thirteen of these elements still exist in HTML 4.
HTML is a markup language that web browsers use to interpret and compose text, images and other material into visual or audible web pages. Default characteristics for every item of HTML markup are defined in the browser, and these characteristics can be altered or enhanced by the web page designer's additional use of CSS. Many of the text elements are found in the 1988 ISO technical report TR 9537 Techniques for using SGML, which in turn covers the features of early text formatting languages such as that used by the RUNOFF command developed in the early 1960s for the CTSS (Compatible Time-Sharing System) operating system: these formatting commands were derived from the commands used by typesetters to manually format documents. However, the SGML concept of generalized markup is based on elements (nested annotated ranges with attributes) rather than merely print effects, with also the separation of structure and processing; HTML has been progressively moved in this direction with CSS.
Berners-Lee considered HTML to be an application of SGML. It was formally defined as such by the Internet Engineering Task Force (IETF) with the mid-1993 publication of the first proposal for an HTML specification: "Hypertext Markup Language (HTML)" Internet-Draft by Berners-Lee and Dan Connolly, which included an SGML Document Type Definition to define the grammar.The draft expired after six months, but was notable for its acknowledgment of the NCSA Mosaic browser's custom tag for embedding in-line images, reflecting the IETF's philosophy of basing standards on successful prototypes.Similarly, Dave Raggett's competing Internet-Draft, "HTML+ (Hypertext Markup Format)", from late 1993, suggested standardizing already-implemented features like tables and fill-out forms.
After the HTML and HTML+ drafts expired in early 1994, the IETF created an HTML Working Group, which in 1995 completed "HTML 2.0", the first HTML specification intended to be treated as a standard against which future implementations should be based.Published as Request for Comments 1866, HTML 2.0 included ideas from the HTML and HTML+ drafts. The 2.0 designation was intended to distinguish the new edition from previous drafts.
Further development under the auspices of the IETF was stalled by competing interests. Since 1996, the HTML specifications have been maintained, with input from commercial software vendors, by the World Wide Web Consortium (W3C). However, in 2000, HTML also became an international standard (ISO/IEC 15445:2000). The last HTML specification published by the W3C is the HTML 4.01 Recommendation, published in late 1999. Its issues and errors were last acknowledged by errata published in 2001.

HTML version timeline

November 24, 1995
HTML 2.0 was published as IETF RFC 1866. Supplemental RFCs added capabilities:
In June 2000, all of these were declared obsolete/historic by RFC 2854.
January 1997
HTML 3.2 was published as a W3C Recommendation. It was the first version developed and standardized exclusively by the W3C, as the IETF had closed its HTML Working Group in September 1996.
HTML 3.2 dropped math formulas entirely, reconciled overlap among various proprietary extensions and adopted most of Netscape's visual markup tags. Netscape's blink element and Microsoft's marquee element were omitted due to a mutual agreement between the two companies. A markup for mathematical formulas similar to that in HTML wasn't standardized until 14 months later in MathML.
December 1997
HTML 4.0was published as a W3C Recommendation. It offers three variations:
  • Strict, in which deprecated elements are forbidden,
  • Transitional, in which deprecated elements are allowed,
  • Frameset, in which mostly only frame related elements are allowed;
Initially code-named "Cougar", HTML 4.0 adopted many browser-specific element types and attributes, but at the same time sought to phase out Netscape's visual markup features by marking them as deprecated in favor of style sheets. HTML 4 is an SGML application conforming to ISO 8879 - SGML.
April 1998
HTML 4.0 was reissued with minor edits without incrementing the version number.
December 1999
HTML 4.01 was published as a W3C Recommendation. It offers the same three variations as HTML 4.0 and its last errata were published May 12, 2001.
May 2000
ISO/IEC 15445:2000 ("ISO HTML", based on HTML 4.01 Strict) was published as an ISO/IEC international standard. In the ISO this standard falls in the domain of the ISO/IEC JTC1/SC34 (ISO/IEC Joint Technical Committee 1, Subcommittee 34 - Document description and processing languages).
As of mid-2008, HTML 4.01 and ISO/IEC 15445:2000 are the most recent versions of HTML. Development of the parallel, XML-based language XHTML occupied the W3C's HTML Working Group through the early and mid-2000s.

October 1991
HTML Tags an informal CERN document listing twelve HTML tags, was first mentioned in public.
June 1992
First informal draft of the HTML DTD, with seven subsequent revisions (July 15, August 6, August 18, November 17, November 19, November 20, November 22)
November 1992
HTML DTD 1.1 (the first with a version number, based on RCS revisions, which start with 1.1 rather than 1.0), an informal draft
June 1993
Hypertext Markup Language was published by the  IIIR Working Group as an Internet-Draft (a rough proposal for a standard). It was replaced by a second version one month later, followed by six further drafts published by IETF itself that finally led to HTML 2.0 in RFC1866
November 1993
HTML+ was published by the IETF as an Internet-Draft and was a competing proposal to the Hypertext Markup Language draft. It expired in May 1994.
April 1995 (authored March 1995)
HTML 3.0 was proposed as a standard to the IETF, but the proposal expired five months later without further action. It included many of the capabilities that were in Raggett's HTML+ proposal, such as support for tables, text flow around figures and the display of complex mathematical formulas.
W3C began development of its own Arena browser as a test bed for HTML 3 and Cascading Style Sheets, but HTML 3.0 did not succeed for several reasons. The draft was considered very large at 150 pages and the pace of browser development, as well as the number of interested parties, had outstripped the resources of the IETF. Browser vendors, including Microsoft and Netscape at the time, chose to implement different subsets of HTML 3's draft features as well as to introduce their own extensions to it. (See Browser wars) These included extensions to control stylistic aspects of documents, contrary to the "belief [of the academic engineering community] that such things as text color, background texture, font size and font face were definitely outside the scope of a language when their only intent was to specify how a document would be organized." Dave Raggett, who has been a W3C Fellow for many years has commented for example, "To a certain extent, Microsoft built its business on the Web by extending HTML features."
January 2008
HTML 5 was published as a Working Draft (link) by the W3C.
Although its syntax closely resembles that of SGML, HTML 5 has abandoned any attempt to be an SGML application and has explicitly defined its own "html" serialization, in addition to an alternative XML-based XHTML 5 serialization.
XHTML is a separate language that began as a reformulation of HTML 4.01 using XML 1.0. It continues to be developed:
  • XHTML 1.0, published January 26, 2000 as a W3C Recommendation, later revised and republished August 1, 2002. It offers the same three variations as HTML 4.0 and 4.01, reformulated in XML, with minor restrictions.
  • XHTML 1.1,published May 31, 2001 as a W3C Recommendation. It is based on XHTML 1.0 Strict, but includes minor changes, can be customized, is reformulated using modules from Modularization of XHTML, which was published April 10, 2001 as a W3C Recommendation.
  • XHTML 2.0,. There is no XHTML 2.0 standard. XHTML 2.0 is incompatible with XHTML 1.x and, therefore, would be more accurately characterized as an XHTML-inspired new language than an update to XHTML 1.x.
  • XHTML 5, which is an update to XHTML 1.x, is being defined alongside HTML 5 in the HTML 5 draft
HTML markup consists of several key components, including elements (and their attributes), character-based data types, character references and entity references. Another important component is the document type declaration, which specifies the Document Type Definition. As of HTML 5, no Document Type Definition will need to be specified and will only determine the layout mode.[41] The Hello world program, a common computer program employed for comparing programming languages, scripting languages and markup languages is made of 9 lines of code although in HTML newlines are optional:
<!doctype html>
<html>
  <head>
    <title>Hello HTML</title>
  </head>
  <body>
    <p>Hello World!</p>
  </body>
</html>
(The text between <html> and </html> describes the web page, and The text between <body> and </body> is the visible page content.) This Document Type Declaration is for HTML 5. If the <!doctype html> declaration is not included, Windows Internet Explorer will render using "quirks mode". HTML documents are composed entirely of HTML elements that, in their most general form have three components: a pair of element tags, a "start tag" and "end tag"; some element attributes within the start tag; and finally, any textual and graphical content between the start and end tags. The HTML element is everything between and including the tags. Each tag is enclosed in angle brackets. The general form of an HTML element is therefore: <tag attribute1="value1" attribute2="value2">content to be rendered</tag> The name of the HTML element is also the name of the tag. Note that the end tag's name is preceded by a slash character, "/". If attributes are not assigned, default values are used. Header of the HTML document:<head>...</head>. Usually the title should be included in the head, for example:
<head>
  <title>The title</title>
</head>
Headings: HTML headings are defined with the <h1> to <h6> tags:
<h1>Heading1</h1>
<h2>Heading2</h2>
<h3>Heading3</h3>
<h4>Heading4</h4>
<h5>Heading5</h5>
<h6>Heading6</h6>
Paragraphs:
<p>Paragraph 1</p>  <p>Paragraph 2</p>
Line breaks:<br>. The difference between <br> and <p> is that 'br' breaks a line without altering the semantic structure of the page, whereas 'p' sections the page into paragraphs. Note also that 'br' is an empty element in that, while it may have attributes, it can take no content or end tag.
<p>This <br> is a paragraph <br> with <br> line breaks</p>
Comments:
<!-- Explanation here -->
Comments can help understanding of the markup and do not display in the webpage. There are several types of markup elements used in HTML.
  • Structural markup describes the purpose of text. For example, <h2>Golf</h2> establishes "Golf" as a second-level heading, which would be rendered in a browser in a manner similar to the "HTML markup" title at the start of this section. Structural markup does not denote any specific rendering, but most web browsers have default styles for element formatting. Text may be further styled with Cascading Style Sheets (CSS).
  • Presentational markup describes the appearance of the text, regardless of its purpose. For example <b>boldface</b> indicates that visual output devices should render "boldface" in bold text, but gives little indication what devices which are unable to do this (such as aural devices that read the text aloud) should do. In the case of both <b>bold</b> and <i>italic</i>, there are other elements that may have equivalent visual renderings but which are more semantic in nature, such as <strong>strong text</strong> and <em>emphasis text</em> respectively. It is easier to see how an aural user agent should interpret the latter two elements. However, they are not equivalent to their presentational counterparts: it would be undesirable for a screen-reader to emphasize the name of a book, for instance, but on a screen such a name would be italicized. Most presentational markup elements have become deprecated under the HTML 4.0 specification, in favor of CSS based styling.
  • Hypertext markup makes parts of a document into links to other documents. An anchor element creates a hyperlink in the document with the href attribute set to the link URL. For example, the HTML markup, <a href="http://en.wikipedia.org/">Wikipedia</a>, will render the word "Wikipedia" as a hyperlink. To render an image as a hyperlink, an 'img' element is inserted as content into the 'a' element. Like 'br', 'img' is an empty element with attributes but no content or closing tag. <a href="http://example.org"><img src="image.gif" alt="descriptive text" width="50" height="50"></a>.
Most of the attributes of an element are name-value pairs, separated by "=" and written within the start tag of an element after the element's name. The value may be enclosed in single or double quotes, although values consisting of certain characters can be left unquoted in HTML (but not XHTML).[43][44] Leaving attribute values unquoted is considered unsafe.[45] In contrast with name-value pair attributes, there are some attributes that affect the element simply by their presence in the start tag of the element,[5] like the ismap attribute for the img element.[46] There are several common attributes that may appear in many elements:
  • The id attribute provides a document-wide unique identifier for an element. This is used to identify the element so that stylesheets can alter its presentational properties, and scripts may alter, animate or delete its contents or presentation. Appended to the URL of the page, it provides a globally unique identifier for the element, typically a sub-section of the page. For example, the ID "Attributes" in http://en.wikipedia.org/wiki/HTML#Attributes
  • The class attribute provides a way of classifying similar elements. This can be used for semantic or presentation purposes. For example, an HTML document might semantically use the designation class="notation" to indicate that all elements with this class value are subordinate to the main text of the document. In presentation, such elements might be gathered together and presented as footnotes on a page instead of appearing in the place where they occur in the HTML source. Class attributes are used semantically in microformats. Multiple class values may be specified; for example class="notation important" puts the element into both the 'notation' and the 'important' classes.
  • An author may use the style attribute to assign presentational properties to a particular element. It is considered better practice to use an element’s id or class attributes to select the element from within a stylesheet, though sometimes this can be too cumbersome for a simple, specific, or ad hoc styling.
  • The title attribute is used to attach subtextual explanation to an element. In most browsers this attribute is displayed as a tooltip.
  • The lang attribute identifies the natural language of the element's contents, which may be different from that of the rest of the document. For example, in an English-language document:
    <p>Oh well, <span lang="fr">c'est la vie</span>, as they say in France.</p>
The abbreviation element, abbr, can be used to demonstrate some of these attributes:
<abbr id="anId" class="jargon" style="color:purple;" title="Hypertext Markup Language">HTML</abbr>
This example displays as HTML; in most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language." Most elements also take the language-related attribute dir to specify text direction, such as with "rtl" for right-to-left text in, for example, 
As of version 4.0, HTML defines a set of 252 character entity references and a set of 1,114,050 numeric character references, both of which allow individual characters to be written via simple markup, rather than literally. A literal character and its markup counterpart are considered equivalent and are rendered identically. The ability to "escape" characters in this way allows for the characters < and & (when written as &lt; and &amp;, respectively) to be interpreted as character data, rather than markup. For example, a literal < normally indicates the start of a tag, and & normally indicates the start of a character entity reference or numeric character reference; writing it as &amp; or &#x26; or &#38; allows & to be included in the content of an element or in the value of an attribute. The double-quote character ("), when used to quote an attribute value, must also be escaped as &quot; or &#x22; or &#34; when it appears within the attribute value itself. Equivalently, the single-quote character ('), when used to quote an attribute value, must also be escaped as &#x27; or &#39; (not as &apos; except in XHTML documents[48]) when it appears within the attribute value itself. If document authors overlook the need to escape such characters, some browsers can be very forgiving and try to use context to guess their intent. The result is still invalid markup, which makes the document less accessible to other browsers and to other user agents that may try to parse the document for search and indexing purposes for example. Escaping also allows for characters that are not easily typed, or that are not available in the document's character encoding, to be represented within element and attribute content. For example, the acute-accented e (é), a character typically found only on Western European keyboards, can be written in any HTML document as the entity reference &eacute; or as the numeric references &#233; or &#xE9;, using characters that are available on all keyboards and are supported in all character encodings. Unicode character encodings such as UTF-8 are compatible with all modern browsers and allow direct access to almost all the characters of the world's writing systems. HTML defines several data types for element content, such as script data and stylesheet data, and a plethora of types for attribute values, including IDs, names, URIs, numbers, units of length, languages, media descriptors, colors, character encodings, dates and times, and so on. All of these data types are specializations of character data. HTML documents are required to start with a Document Type Declaration (informally, a "doctype"). In browsers, the doctype helps to define the rendering mode—particularly whether to use quirks mode. The original purpose of the doctype was to enable parsing and validation of HTML documents by SGML tools based on the Document Type Definition (DTD). The DTD to which the DOCTYPE refers contains a machine-readable grammar specifying the permitted and prohibited content for a document conforming to such a DTD. Browsers, on the other hand, do not implement HTML as an application of SGML and by consequence do not read the DTD. HTML 5 does not define a DTD, because of the technology's inherent limitations, so in HTML 5 the doctype declaration, <!doctype html>, does not refer to a DTD. An example of an HTML 4 doctype is
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
This declaration references the DTD for the 'strict' version of HTML 4.01. SGML-based validators read the DTD in order to properly parse the document and to perform validation. In modern browsers, a valid doctype activates standards mode as opposed to quirks mode. In addition, HTML 4.01 provides Transitional and Frameset DTDs, as explained below. Semantic HTML is a way of writing HTML that emphasizes the meaning of the encoded information over its presentation (look). HTML has included semantic markup from its inception,[50] but has also included presentational markup such as <font>, <i> and <center> tags. There are also the semantically neutral span and div tags. Since the late 1990s when Cascading Style Sheets were beginning to work in most browsers, web authors have been encouraged to avoid the use of presentational HTML markup with a view to the separation of presentation and content.[51] In a 2001 discussion of the Semantic Web, Tim Berners-Lee and others gave examples of ways in which intelligent software 'agents' may one day automatically trawl the Web and find, filter and correlate previously unrelated, published facts for the benefit of human users.[52] Such agents are not commonplace even now, but some of the ideas of Web 2.0, mashups and price comparison websites may be coming close. The main difference between these web application hybrids and Berners-Lee's semantic agents lies in the fact that the current aggregation and hybridisation of information is usually designed in by web developers, who already know the web locations and the API semantics of the specific data they wish to mash, compare and combine. An important type of web agent that does trawl and read web pages automatically, without prior knowledge of what it might find, is the Web crawler or search-engine spider. These software agents are dependent on the semantic clarity of web pages they find as they use various techniques and algorithms to read and index millions of web pages a day and provide web users with search facilities without which the World Wide Web would be only a fraction of its current usefulness. In order for search-engine spiders to be able to rate the significance of pieces of text they find in HTML documents, and also for those creating mashups and other hybrids as well as for more automated agents as they are developed, the semantic structures that exist in HTML need to be widely and uniformly applied to bring out the meaning of published text.[53] Presentational markup tags are deprecated in current HTML and XHTML recommendations and are illegal in HTML 5. Good semantic HTML also improves the accessibility of web documents (see also Web Content Accessibility Guidelines). For example, when a screen reader or audio browser can correctly ascertain the structure of a document, it will not waste the visually impaired user's time by reading out repeated or irrelevant information when it has been marked up correctly. HTML documents can be delivered by the same means as any other computer file. However, they are most often delivered either by HTTP from a web server or by email. The World Wide Web is composed primarily of HTML documents transmitted from web servers to web browsers using the Hypertext Transfer Protocol (HTTP). However, HTTP is used to serve images, sound, and other content, in addition to HTML. To allow the Web browser to know how to handle each document it receives, other information is transmitted along with the document. This meta data usually includes the MIME type (e.g. text/html or application/xhtml+xml) and the character encoding (see Character encoding in HTML). In modern browsers, the MIME type that is sent with the HTML document may affect how the document is initially interpreted. A document sent with the XHTML MIME type is expected to be well-formed XML; syntax errors may cause the browser to fail to render it. The same document sent with the HTML MIME type might be displayed successfully, since some browsers are more lenient with HTML. The W3C recommendations state that XHTML 1.0 documents that follow guidelines set forth in the recommendation's Appendix C may be labeled with either MIME Type.[54] The current XHTML 1.1 Working Draft also states that XHTML 1.1 documents should[55] be labeled with either MIME type.[56] ost graphical email clients allow the use of a subset of HTML (often ill-defined) to provide formatting and semantic markup not available with plain text. This may include typographic information like coloured headings, emphasized and quoted text, inline images and diagrams. Many such clients include both a GUI editor for composing HTML e-mail messages and a rendering engine for displaying them. Use of HTML in e-mail is controversial because of compatibility issues, because it can help disguise phishing attacks, because it can confuse spam filters and because the message size is larger than plain text. The most common filename extension for files containing HTML is .html. A common abbreviation of this is .htm, which originated because some early operating systems and file systems, such as DOS and FAT, limited file extensions to three letters. An HTML Application (HTA; file extension ".hta") is a Microsoft Windows application that uses HTML and Dynamic HTML in a browser to provide the application's graphical interface. A regular HTML file is confined to the security model of the web browser, communicating only to web servers and manipulating only webpage objects and site cookies. An HTA runs as a fully trusted application and therefore has more privileges, like creation/editing/removal of files and Windows Registry entries. Because they operate outside the browser's security model, HTAs cannot be executed via HTTP, but must be downloaded (just like an EXE file) and executed from local file system. Since its inception, HTML and its associated protocols gained acceptance relatively quickly. However, no clear standards existed in the early years of the language. Though its creators originally conceived of HTML as a semantic language devoid of presentation details,[58] practical uses pushed many presentational elements and attributes into the language, driven largely by the various browser vendors. The latest standards surrounding HTML reflect efforts to overcome the sometimes chaotic development of the language[59] and to create a rational foundation for building both meaningful and well-presented documents. To return HTML to its role as a semantic language, the W3C has developed style languages such as CSS and XSL to shoulder the burden of presentation. In conjunction, the HTML specification has slowly reined in the presentational elements. There are two axes differentiating various variations of HTML as currently specified: SGML-based HTML versus XML-based HTML (referred to as XHTML) on one axis, and strict versus transitional (loose) versus frameset on the other axis. One difference in the latest HTML specifications lies in the distinction between the SGML-based specification and the XML-based specification. The XML-based specification is usually called XHTML to distinguish it clearly from the more traditional definition. However, the root element name continues to be 'html' even in the XHTML-specified HTML. The W3C intended XHTML 1.0 to be identical to HTML 4.01 except where limitations of XML over the more complex SGML require workarounds. Because XHTML and HTML are closely related, they are sometimes documented in parallel. In such circumstances, some authors conflate the two names as (X)HTML or X(HTML). Like HTML 4.01, XHTML 1.0 has three sub-specifications: strict, loose and frameset. Aside from the different opening declarations for a document, the differences between an HTML 4.01 and XHTML 1.0 document—in each of the corresponding DTDs—are largely syntactic. The underlying syntax of HTML allows many shortcuts that XHTML does not, such as elements with optional opening or closing tags, and even EMPTY elements which must not have an end tag. By contrast, XHTML requires all elements to have an opening tag and a closing tag. XHTML, however, also introduces a new shortcut: an XHTML tag may be opened and closed within the same tag, by including a slash before the end of the tag like this: <br/>. The introduction of this shorthand, which is not used in the SGML declaration for HTML 4.01, may confuse earlier software unfamiliar with this new convention. A fix for this is to include a space before closing the tag, as such: <br />.[60] To understand the subtle differences between HTML and XHTML, consider the transformation of a valid and well-formed XHTML 1.0 document that adheres to Appendix C (see below) into a valid HTML 4.01 document. To make this translation requires the following steps:
  1. The language for an element should be specified with a lang attribute rather than the XHTML xml:lang attribute. XHTML uses XML's built in language-defining functionality attribute.
  2. Remove the XML namespace (xmlns=URI). HTML has no facilities for namespaces.
  3. Change the document type declaration from XHTML 1.0 to HTML 4.01. (see DTD section for further explanation).
  4. If present, remove the XML declaration. (Typically this is: <?xml version="1.0" encoding="utf-8"?>).
  5. Ensure that the document’s MIME type is set to text/html. For both HTML and XHTML, this comes from the HTTP Content-Type header sent by the server.
  6. Change the XML empty-element syntax to an HTML style empty element (<br/> to <br>).
Those are the main changes necessary to translate a document from XHTML 1.0 to HTML 4.01. To translate from HTML to XHTML would also require the addition of any omitted opening or closing tags. Whether coding in HTML or XHTML it may just be best to always include the optional tags within an HTML document rather than remembering which tags can be omitted. A well-formed XHTML document adheres to all the syntax requirements of XML. A valid document adheres to the content specification for XHTML, which describes the document structure. The W3C recommends several conventions to ensure an easy migration between HTML and XHTML (see HTML Compatibility Guidelines). The following steps can be applied to XHTML 1.0 documents only:
  • Include both xml:lang and lang attributes on any elements assigning language.
  • Use the empty-element syntax only for elements specified as empty in HTML.
  • Include an extra space in empty-element tags: for example <br /> instead of <br/>.
  • Include explicit close tags for elements that permit content but are left empty (for example, <div></div>, not <div />).
  • Omit the XML declaration.
By carefully following the W3C’s compatibility guidelines, a user agent should be able to interpret the document equally as HTML or XHTML. For documents that are XHTML 1.0 and have been made compatible in this way, the W3C permits them to be served either as HTML (with a text/html MIME type), or as XHTML (with an application/xhtml+xml or application/xml MIME type). When delivered as XHTML, browsers should use an XML parser, which adheres strictly to the XML specifications for parsing the document's contents. HTML 4 defined three different versions of the language: Strict, Transitional (once called Loose) and Frameset. The Strict version is intended for new documents and is considered best practice, while the Transitional and Frameset versions were developed to make it easier to transition documents that conformed to older HTML specification or didn't conform to any specification to a version of HTML 4. The Transitional and Frameset versions allow for presentational markup, which is omitted in the Strict version. Instead, cascading style sheets are encouraged to improve the presentation of HTML documents. Because XHTML 1 only defines an XML syntax for the language defined by HTML 4, the same differences apply to XHTML 1 as well. The Transitional version allows the following parts of the vocabulary, which are not included in the Strict version:
  • A looser content model
    • Inline elements and plain text are allowed directly in: body, blockquote, form, noscript and noframes
  • Presentation related elements
    • underline (u)
    • strike-through (s)
    • center
    • font
    • basefont
  • Presentation related attributes
    • background and bgcolor attributes for body element.
    • align attribute on div, form, paragraph (p) and heading (h1...h6) elements
    • align, noshade, size and width attributes on hr element
    • align, border, vspace and hspace attributes on img and object elements
    • align attribute on legend and caption elements
    • align and bgcolor on table element
    • nowrap, bgcolor, width, height on td and th elements
    • bgcolor attribute on tr element
    • clear attribute on br element
    • compact attribute on dl, dir and menu elements
    • type, compact and start attributes on ol and ul elements
    • type and value attributes on li element
    • width attribute on pre element
  • Additional elements in Transitional specification
    • menu list (no substitute, though unordered list is recommended)
    • dir list (no substitute, though unordered list is recommended)
    • isindex (element requires server-side support and is typically added to documents server-side, form and input elements can be used as a substitute)
    • applet (deprecated in favor of object element)
  • The language attribute on script element (redundant with the type attribute).
  • Frame related entities
    • iframe
    • noframes
    • target attribute on anchor, client-side image-map (imagemap), link, form and base elements
The Frameset version includes everything in the Transitional version, as well as the frameset element (used instead of body) and the frame element. In addition to the above transitional differences, the frameset specifications (whether XHTML 1.0 or HTML 4.01) specifies a different content model, with frameset replacing body, that contains either frame elements, or optionally noframes with a body. As this list demonstrates, the loose versions of the specification are maintained for legacy support. However, contrary to popular misconceptions, the move to XHTML does not imply a removal of this legacy support. Rather the X in XML stands for extensible and the W3C is modularizing the entire specification and opening it up to independent extensions. The primary achievement in the move from XHTML 1.0 to XHTML 1.1 is the modularization of the entire specification. The strict version of HTML is deployed in XHTML 1.1 through a set of modular extensions to the base XHTML 1.1 specification. Likewise, someone looking for the loose (transitional) or frameset specifications will find similar extended XHTML 1.1 support (much of it is contained in the legacy or frame modules). The modularization also allows for separate features to develop on their own timetable. So for example, XHTML 1.1 will allow quicker migration to emerging XML standards such as MathML (a presentational and semantic math language based on XML) and XForms—a new highly advanced web-form technology to replace the existing HTML forms. In summary, the HTML 4.01 specification primarily reined in all the various HTML implementations into a single clearly written specification based on SGML. XHTML 1.0, ported this specification, as is, to the new XML defined specification. Next, XHTML 1.1 takes advantage of the extensible nature of XML and modularizes the whole specification. XHTML 2.0 will be the first step in adding new features to the specification in a standards-body-based approach. HTML lacks some of the features found in earlier hypertext systems, such as typed links, source tracking, fat links and others.[61] Even some hypertext features that were in early versions of HTML have been ignored by most popular web browsers until recently, such as the link element and in-browser Web page editing. Sometimes Web services or browser manufacturers remedy these shortcomings. For instance, wikis and content management systems allow surfers to edit the Web pages they visit. There are some WYSIWYG editors (What You See Is What You Get), in which the user lays out everything as it is to appear in the HTML document using a graphical user interface (GUI), where the editor renders this as an HTML document, no longer requiring the author to have extensive knowledge of HTML. The WYSIWYG editing model has been criticized,[62][63] primarily because of the low quality of the generated code; there are voices advocating a change to the WYSIWYM model. WYSIWYG editors remains a controversial topic because of their perceived flaws such as:
  • Relying mainly on layout as opposed to meaning, often using markup that does not convey the intended meaning but simply copies the layout.[64]
  • Often producing extremely verbose and redundant code that fails to make use of the cascading nature of HTML and CSS.
  • Often producing ungrammatical markup often called tag soup.
  • As a great deal of information of HTML documents is not in the layout, the model has been criticized for its 'what you see is all you get'-nature.[65]
Nevertheless, since WYSIWYG editors offer convenience over hand-coded pages as well as not requiring the author to know the finer details of HTML, they still dominate web authoring.