Top 10 Validation Results - Out of the 745 home page documents being monitored, the Guardian.co.uk ranked № 2 in the HTML/XHTML Error and Warnings Categories on 2009-10-12 at 05:34. News Websites Comparisons
2009-10-12 - Edward, I challenge you! Take the website home page document with the most HTML/XHTML Validation Errors and Warnings and validate it!
To the person (to remain anonymous) who originally challenged me, I believe I've met and have exceeded all stipulations imposed when the challenge was first presented. Those were...
My validation testing and personal challenge is based on the Guardian's Home Page Document as of 2009-10-12 at 05:34 as shown below and also available as part of the Validation History in our Showdown.

Unfortunately due to the sheer volume of Errors and Warnings encountered, the Semantic Data Extractor Tool from the W3 is unable to correctly parse the home page document for the Guardian. Link to SDE Results
I spent approximately 1.5 hours reformatting and cleaning up the HTML/XHTML for the home page document of the Guardian. Many of the 2,309 Errors and 1,356 Warnings encountered were due to invalid naming conventions being used on anchors. These were cascading errors which once corrected, brought the total numbers of Errors to less than 500 and eliminated ALL Warnings.

Preview the Guardian in XHMTL 1.0 Strict Mode
The validation time could have been reduced to approximately 1.0 hours if I had access to the main templates and made changes to one reference instead of 300+ that were each unique (due to dynamics) and required special Find and Replace queries.
Check this out! I was able to extract a complete and well structured Document Outline after cleaning up the invalid code. Link to SDE Results
Many of you are asking why I would spend my valuable time literally dissecting 8,356 lines of code which contained 178,515 bytes of information, including white space. Remember, one white space is equal to 1 byte. Unused and excess white space adds to the overall equation. 3,458 of the above 8,356 lines of code are blank.
I wanted to make a point when it comes to the time and level of complexity involved with validating a document. If I can take the Guardian's home page which had 2,309 Errors and 1,356 Warnings at the time I began my test, and validate it within 1.5 hours, you too can do the same. This is NOT rocket science as they say and can be easily achieved using the correct tools and, using those tools correctly.
The Guardian could easily set a new benchmark in online publishing from a technical perspective. The HTML/XHTML Errors and Warnings you see in the reports are simplistic in nature. Unfortunately because they are related to anchor functions, changing the naming conventions on those may present a daunting task to the Webmasters.
<a href="" name="&lid={}{}&lpos={}{1}">
Is it possible that you violated the naming convention for the "name" attribute?
This validator checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc. If you wish to validate specific content such as RSS/Atom feeds or CSS stylesheets, MobileOK content, or to find broken links, there are other validators and tools available.
The Web Developer extension adds a menu and a toolbar to the browser with various web developer tools. After installing the extension there is a 'Web Developer' menu under the 'Tools' and context menu of the browser, as well as a new toolbar.
This tool, geared by an XSLT stylesheet, tries to extract some information from a HTML semantic rich document. It only uses information available through a good usage of the semantics defined in HTML.
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