Google: it’s Better if your Web Pages have Valid HTML
Google’s John Mueller said in a Google Hangout that it is better to have a website with valid HTML. “This came up recently with the change of the guidelines, with regards to change made in the webmaster guidelines. We mentioned ‘use valid HTML’. The question here is: is the W3C Validation (Broken HTML) ranking factor or should we care about it?
It is not directly a ranking factor. It is not the sense that if your site is not using valid HTML we will remove it from he index. Because I think we will have a pretty empty search results.
But there are a few aspects there that do come into play. On the one hand, a site with really broken HTML, something that we see really rarely, then it is really hard for us to crawl it and index the content because we can’t pick it up.
The other two aspects which are kind more in regards to structured data. Sometimes it is really hard to pick up the structured data when the HTML is broken completely. So you can’t easily use a validator for the structured data.
The other thing is in regards to mobile devices and cross browser support is if you have broken HTML then that is sometimes really hard to render on newer devices.”