Matt Cutts, Google’s head of search spam, answers a question about text formatting in his latest video where a user writes in to ask:
“In terms of SEO, what is the difference between <strong> tag and <b> tag for emphasis on certain words of text. From the user perspective, both tags have the same effect (words in bold). Which tags should we use in which circumstances?”
This is a throwback question from 2006 when Matt assured us that, when it comes to SEO best practices, there is no difference between using <strong> or <b> tags. Both tags get treated the exact same in terms of ranking and how pages are indexed. In the video Cutts recalled answering this question while adding that there is also no difference between <em> and <i> tags when it comes to ranking, scoring and other search factors. Matt was somewhat vague in his response, saying things may have changed since 2006, “but I really kind of doubt it.” You can use either one and Matt says there won’t be any difference when it comes to Google ranking. Matt says that the only difference between the two tags is that that <strong> tag refers to presentation, while the <b> tag is a semantic label. But he reminds us that in practice they both do the same thing, every browser just uses the tags to make text bold. Matt ends the video by reassuring us not to worry about it. Go ahead and use whatever you prefer.
Source : searchenginejournal.com/matt-cutts-strong-bold-tags-seo/74073/#0X6GjvpFfcY60G16.99