Valid XHTML for SEO

Introduction

According to a study made by Opera [1], only around 4% of the web is using valid (X)HTML. This is a surprising result as it is usually fairly simple to fix. Browsers can correctly determine some errors and work around them such as the odd missing paragraph tag and so on.

With SEO every factor can make a difference in the ranking so it is important that you give you page the opportunity to be ranked. If you do not do use valid code, there is a possibility that your code may be misinterpreted by the search engine spiders and the rest of your SEO work will be in vain. In the ranking process it is also highly likely, other things being equal, that the search engines would display a page which is semantically valid. In addition valid code is more likely to display correctly in every browser except IE6 which has its own ’special’ ways of interpreting code and CSS.

What do we Mean by Valid code?

Code is valid if it passes the W3C.org validation test. Here the W3C provide validators for XHTML, CSS, RDF RSS and Semantics. When your pages passes validation, as SEO the Game does, you can place an icon to show that you have made the effort.

Does Valid Code make a Difference?

Several sites have tried to carry out independent tests. However, as we know, in trying to create a fair experiment by minimising the number of variables,  we are affecting the result because of duplicate content.

• Marketingdefined: Valid HTML Code Crucial to SEO
• New Sun Graphics: Why Valid Source Code Matters for SEO
• hobo-web.co.uk: SEO Test – Google Prefers Valid HTML & CSS

Taking the opposite view, valid code is not important.

• Searchenginejournal: W3C Compliance Impact on SEO en SEO & Importance of Valid Source Code (W3C validation)
• SEOContest2008: W3C Code Validation is NOT Important In Search Engine Ranking

I would still argue that if you do not pay attention to validation there is a possibility that  your ranking might be harmed and if you do validate your pages, it isn’t going to cause you to lose rankings. So it is a question of how much effort (money) you are willing to put into a site.

The first few occasions you have to validate a site it can be time consuming to fix but it soon becomes easier to interpret the errors and in the future you will remember not to make the errors in the first place.

Common W3C Validation Problems

The most common errors that I find when validating code include:

• characters such as & in dynamic URLs which should be coded as &
• divs that don’t correspond to their closing <divs>,
• JavaScript being mistaken for HTML. This be corrected by wrapping the JavaScript in CDATA tags:

  <![CDATA[    ]]>

• divs that use the id attributes when there is more than one instance. CSS classes should be used instead.