If you’re a regular web user, you have no doubt seen those two little links at the bottom of a webpage. Often they have ticks next to them or are in little yellow boxes with the characters “W3C”, or they’re just plain text:

xHTML 1.0 Yellow CSS Yellow 2
xHTML Green CSS Green
xHTML 1 Grey CSS 2.0 Grey
xHTML 1.0 Blue CSS Medium Blue
xHTML blue CSS Blue
CSS 2.0 Grey1 CSS Grey

So what do they all mean?

Let’s begin with the W3C - World Wide Web Consortium.

The World Wide Web Consortium (W3C) is an international consortium where Member organisations, a full-time staff, and the public work together to develop Web standards. W3C’s mission is:

To lead the World Wide Web to its full potential by developing protocols and guidelines that ensure long-term growth for the Web.


A website is typically programmed (aka: coded) in a computer language known as HTML (HyperText Markup Language) and many of those standards (or “guidelines”) provide recommendations on how you should program your website. And just like every other language, there are rules which govern its structure - such as with English: vocabulary, grammar, syntax and spelling. The W3C has an online program which can check if a website has been coded correctly and has followed all the rules of that language. This program is called a ‘validator’ and after checking a website, it will give you a result: typically “this website is valid” or “this website is invalid“.

A website author/owner often puts a link, such as “valid HTML”, which links directly to the W3C Validator. The W3C Validator will check the code of that website and tell you if it is valid or invalid.

OK, so that covers the “valid” part, but why does it sometimes say “valid CSS” or “valid xHTML 1.1 Strict”?

There is more than one language a website can be programmed in (I won’t go into which is the better to use), but one of those languages is xHTML and it comes in several versions. This blog uses xHTML 1.0 Transitional [click here to check the validity of this blog's xHTML]. Another language used to help render the webpage is CSS - Cascading Style Sheets. The W3C can check the CSS for validity and again there is more than one version of CSS [check that this blog uses valid CSS].

Side Note: If you have read a previous post on this blog - Web 2.0 “… linking people”, you will know that a ‘Web 2.0′ webpage should have its form separate from its content. xHTML and CSS were invented to serve this very purpose. xHTML is supposed to define the content and CSS is supposed to define the form.

There you have it. Now when you’re walking down the street and someone stops to ask you what those little icons on a webpage mean, you’ll have an answer for them.

Side Fact: Tim Berners-Lee is the W3C Director and also the inventor of the World Wide Web (no, the Web isn’t a miraculous gift from the heavens, in 1989 a guy named Tim actually invented it). Read more about it here…

This entry was posted on Sunday, March 9th, 2008 at 8:45 pm and is filed under Internet. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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