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How important is valid HTML for search engine rankings?

Posted on by Clive Walker in Google Search Engines

I wrote this post a while back. The content can still be relevant but the information I've linked to may not be available.

There’s a lot of discussion in web designer/developer circles about valid HTML and search engine rankings. If your site has valid HTML or XHTML, will it have better search engine rankings than a website with HTML errors and warnings? My answer would be ‘Yes’.

However, I will qualify my positive statement by saying that I don’t know how you could prove this. My ‘Yes’ answer is based on my experience of website redesigns over the last couple of years. In each case, the new website followed better coding standards and an improved search engine position was achieved over several months. However, there are undoubtedly a lot of other factors involved here (including better semantics) and my experience may be just good luck. I’d have to put my answer down to gut feeling rather than scientifically proven.

There’s an interesting article about valid HTML and search engine rankings in a recent Entireweb newsletter. The author searched specific keywords and checked the top ranked websites for valid HTML using this Firefox HTML validator extension. Results showed that most of the websites did not validate. In fact, only 7 of 150 websites validated!

Update: Online version of Entireweb article on valid HTML and SE rankings

The apparent answer here is that valid HTML does not matter two hoots. However, I don’t think you can say that for certain unless you can compare identical websites where the only difference is valid HTML/non-valid HTML. This looks difficult to prove particularly if search engines penalise duplicate content.

Oh well. Back to my gut feeling. I’d still say that valid HTML/XHTML is important.

PS Google says ‘check for correct HTML’ in its webmaster guidelines

· Related » Mike Davidson has investigated how web standards (and other factors) affect Google placement in his Roundabout SEO Test aka the lodefizzle test.

One of Mike’s conclusions is “It’s not clear that validity helps search engine ranking, but it’s definitely true that certain errors in your code can get you completely removed from indexes”.

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  • 12 Jul 2006 23:56:55

    Whether it is good for search engines or not, your code should always be valid. I can’t see how it would get you removed from search engines though. The statistic of only 7 out of 150 websites being valid is amazing and I find it easy to believe.

  • 13 Jul 2006 08:05:35

    Craig: In Mike D’s test, he missed a closing ” from a table attribute to make the table invalid – which caused the page to not render in most browsers. As a result, Google did not index the page. Admittedly, this is only one example.

    I was also surprised by the low number of validated websites in the 150, particularly since a lot of these would (presumably) be companies who have spent some time (and money) getting to the top of the search listings.

    On the other hand, it’s difficult to get true validity if third party code (eg Google AdSense) does not validate.

  • 23 Jun 2007 15:00:49

    Valid HTML is certainly very important – we should treat it as importantly as an RSS Feed being properly formatted! – Valid HTML means faster responses and loads within web browsers. Valid HTML also allows browsers to detect and correctly display any content based on the DTD of the standard. There are no advantages to not using valid HTML – but why not just use valid XHTML a more correct standard

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