In his latest webmaster video, Matt Cutts has answered a question related to text formatting.
The question asked to Cutts was: "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"?
The video is a 2006 throwback, when Matt assured that there is no difference between using <b> or <strong> tags for SEO best practices.
Recalling his answer, Matt said "things might have changed since 2006, but I kind of doubt it". At that time, Cutts said that there was no difference in how Google treated <strong> and <b> tag, when it comes to ranking, scoring, or other search factors. Adding to his previously answered question, Matt said that same is true for <em> and <i> tags, when you are using italics.
Cutts clarified the difference between the two tags. He explained that <strong> tag technically talks about presentation. The <b> tag is a semantic label. Cutts also said that however in practice, every browser makes it bold.
In the end of the video, Matt has assured webmasters not to worry about it and use whatever they prefer.Matt Cutts on Difference Between "b" and "strong" tags, in Terms of SEO!,