Is W3C validation relevant to SEO?

December 26, 2006

Part of the SEO process we perform on websites is to make sure that they pass W3C standards. The W3C is an organization that issues a set of standards that allow programmers and web designers to make websites that are compatible with as many technologies as possible, this is called Web Interoperability. Making sure that your site is valid ensures that the search engine spiders can navigate the site properly and parse all of the text that is there.

However, in doing a bit of research I have noticed that some major sites are not valid. Many of the search engine websites have up to 50 errors and some of the more well known shopping sites have over 1000 errors.

Address	Site	Validation Errors
www.amazon.co.uk	Amazon	1128
www.play.com	Play	300
www.ebay.co.uk	Ebay	217
www.dogpile.com	Dogpile	78
www.google.co.uk	Google	50
www.cnn.com	CNN	38
www.bbc.co.uk	BBC	37
www.yahoo.com	Yahoo	37
www.altavista.com	Alta Vista	37
www.adobe.com	Adobe	14
www.microsoft.com	Microsoft	5
www.justsearching.co.uk	JustSearch	0
www.dmoz.org	Dmoz	0
www.mozilla.org	Mozilla	0
www.msn.com	MSN	0

So is validation useful in search engine optimisation? Validation on it’s own may not be a major factor in page rankings. However, a page that has valid, standards compliant code will probably rank higher than one that isn’t as invalid code might cause some problems with spiders interpreting the page.

I am of the opinion that compliance with web standards is essential in any web site or web based product. It ensures that the site is accessible to people and machines and that the site will function with the advent of new browsers. The second point is a work based point as it stops developers having to redesign their sites every time a new browser comes out. The first point, that of accessibility, should be at the forefront of every website developers mind as sites that are not accessible do not conform to the UK Disability Discrimination Act. Part three of this act refers to the provision of goods, facilities and services, which specifically mentions websites. So if your site does not conform to at least level 2 of the Web Content Accessibility Guidelines (which includes validation) you will in breach of the act and in danger of being fined or even sued.

The U.S.A. has an equivalent law called Section 508.

Philip Norton BSc MSc
SEO Engineer