Conventional wisdom says that using bold (<b> or <strong> in HTML) or italics (<em> or <i> in HTML) around keywords you want your page to rank for will improve SEO. Some “SEO experts” will tell you the same—that selective use of bold and italics on keywords will improve your rankings. (Digression: read why anyone who calls themselves an SEO should make you leery.)
Is there any actual data to indicate this really is a good practice?
In search of an answer
SEOMoz publishes their Search Engine Ranking Factors once every two years. This is the most comprehensive study I’m aware of that looks at the question of what actually works in SEO. However, even they can only guess at the effectiveness of this tactic.
In their section on Page-level Keyword Usage, they didn’t measure actual, observed correlation between bold/italicized keywords and search rankings (I suspect because they couldn’t—if there is a correlation, it’s likely infinitesimal).
Instead, they asked SEO “experts” to rate how important they thought this feature was. Even with that, shall we say, less than rigorous methodology (read as: dubious and self-reinforcing), bold and italics ranked near the bottom of the list, as the 15th most important page-level factor. Thus, what evidence there is for bolding and italicizing keywords is shaky at best.
Nonetheless, I still recommend doing it.
The real impact of bold and italics on SEO
As I’ve written before, it’s increasingly true that search engines value pages the same way humans would (and do). If you create a page that has spectacular information on its topic, you’ll be rewarded for it in the search rankings. Part of having a great web page is that the content is easily consumable by readers. To this end, putting important words and phrases in bold or italics will make your pages easier to read.
Furthermore, a large component—probably the largest component—of search engine rankings is links to your page from other influential web sites. By making your pages easier to read (and scan), you’ll be improving the user’s experience with your content, and thus increasing the likelihood of those users linking back to your page.
This indirect method of improving search engine rankings (SEO) is the only way I believe bold and italics will affect your page. In fact, this is the only data-supported way that these factors might affect SEO.
Moreover, this doesn’t just apply to bold or italicized keywords; instead, you should use bold and italics throughout your copy in any way that improves the readability of your text.
More Resources
- The Bible of Web usability—Don’t Make Me Think by Steve Krug. Want to make your pages more readable (and thus more linkable, more searchable, and so on)? Read Don’t Make Me Think and take Krug’s insight to heart.
- On-page SEO for Small Companies, from Patrick McKenzie of Kalzumeus. This is very actionable advice for most small business Web sites (heck, most large businesses could learn a thing or two as well!). Patrick is one of those rarified SEO experts (note the lack of quotes—he’s not just an “expert”!) whose blog posts are consistently worth reading.