Valid HTML is important - right? We are told every day in the website owner community that valid HTML code is the 'right' way to build your website. Valid HTML allows for greater accessibility, cross-browser compatability, and can even possibly help your search engine rankings.

But then again...

I decided to test whether valid HTML can actually help your rankings in Google. A lot of website owners talk about how their non-compliant websites do well in Google and how their complaint sites may not be doing as well. The implied suggestion here is that Google either simply did not care about errors in HTML, or even more extreme, that Google preferred non-compliant websites - a charge that would certainly be puzzling if it were true.

A Sneak Peak at Results - Google Preferred Invalid HTML?

The results of my test surprised me. Not only did I find that Google apparantly does not give any preference to sites with valid HTML, Google actually seemed to prefer the sites with blatant errors in their code.

Think about this - if Google does give preference to websites with errors in their HTML, then it would actually benefit you to program errors into your website (as far as the SEO is concerned). Now I am not ready to accept that as a valid conclusion, but the results are what they are. With these conclusions staring back at us, I though it necessary to publish the methodology and results, and open up the topic for discussion.

Setting Up the Study

As we all know, Google does not rely on any one factor to rank a website. As a result, a website could be horribly optimized in one aspect of their website, but still reach the top of the rankings because they are well optimized elsewhere. This makes testing individual aspects of SEO tricky.

In order to determine whether valid HTML was actually a factor that contributed to your ranking, even in the smallest of ways, it was necessary to isolate every other aspect that could possibly influence the ranking of a website. To do this, I looked to do the following things:

- The keyword density had to be identical
- The page size should be identical (just in case this effected the crawlability)
- The competing websites should be newly registered domains, all registered on the same day (removing age of site from the equation)
- The competing websites should be hosted on the same server
- Inbound links should be identical and from the same site so as to avoid different link weightings
- The links should have identical anchor text
- Since all the links would come in to the same site, link order might affect rankings - this would need to be neutralized
- The content should be identical so as not to influence the rankings in any other way (possible poison pill - I'll explain later)

The only difference between the two sites would be that one would be made with valid HTML and the other would be made with obvious, and significant, errors in the HTML.

My initial thought was to have just two competing websites both trying to rank for the same non-sense keyword (the keyword would be one that currently has no rankings in Google). The idea was to get a snapshot of how Google initially ranked the websites. But there was a problem.

To read more on this subject, click here.