Multiple H1 Tags and SEO

Yesterday, I had a conversation with my boss about the use of multiple <h1> tags in the default WordPress theme and their effect on SEO. I contended that extra <h1> tags, when properly used, will not effect SEO, while he claimed that a page can have one and only one <h1>. In WordPress the site title is enclosed in an <h1> tag while page and post titles are also in <h1>s.

I pointed out that HTML5 sectioning elements, such as <header> in the case of WordPress, are designed to have their heading tags relative to the section they are in. So a <header> can have an <h1> and other elements such as the <article> or <section> can as well. This allows for different parts of a page to have independent hierarchies.

His point was that the single <h1> on the page will give a search engine the best idea of the contents of the page. It acts as a thesis sentence for the page.

Semantically, I think this is a matter of style. I can see using the main heading of a site to put forth the main idea for the page. However, with HTML5′s new outlining and sectioning model you can think of the entire site itself as being at the top of the hierarchy. This means that using an <h1> for the site title provides the highest level label for the site.

All of this is good, but what about Google? Does the additional usage of <h1> tags adversely effect search rankings? According to this video from Matt Cutts at Google, the answer is no as long as they are not used excessively or unscrupulously.

Since semantically it doesn’t matter and SEO is unaffected either way, it really is a matter of style. In any case, it wasn’t worth an argument.