HTML validation & SEO

HTML validation and Google’s web-search … validation isn’t necessary for crawling, indexing, or ranking, as we’ve said [1] many times in the past. However, if you have problems with meta-tags, structured data, or link-elements (for example, if your hreflang markup isn’t being picked up properly), then using a HTML validator can sometimes point you at problems in your markup. In a recent example, a site was accidentally including a banner in the HEAD of a page.