HTML and CSS Reference
Validating a Website for HTML5 Compliance
To verify how well a website supports HTML5, we can use an HTML5 validator tool.
There are many online tools available, but the one that conforms to the most recent HTML5
specifications is the W3C Markup Validation Service available at http://validator.w3.org.
The W3C Markup Validation Service enables us to verify a website against non-English
character-encoding types and even older markup languages, such as HTML versions 4.01,
3.2, and 2.0, various XHTML standards, MathML, Scalable Vector Graphics (SVG), and
Synchronized Multimedia Integration Language (SMIL).
To use the W3C Markup Validation Service, the web page to be tested has to be published
online. To use this tool, we submit the URL address of the web page, and the tool downloads
the HTML source code for the site, auto-detects the encoding and document type, and ana-
lyzes the page for compliance. The registered infractions are categorized like errors and
warnings and are rated by severity. The tool even offers explanations and possible solutions
to the noted problems.
Even if an HTML5 web page fails validation, it may still render correctly in a web browser.
This is because the HTML5 specifications state that web developers must avoid deprecated
tags, but web browsers may honor them. This is a critical requirement of maintaining back-
ward compatibility with earlier HTML versions and web pages that have not been updated
to the latest standard.
With all of the interventions thus far, our sample CV should now have the following HTML
<!--[if lt IE 9]>