gouri - 3:57 pm on Sep 17, 2012 (gmt 0)
I have read that what is looked at by the search engines is the tags (e.g. h1, h2) that a phrase is in.
If you have keywords in an h2 tag, for example, and it is similar in size to your body text, the fact that the words are in an h2 tag will give them more importance. The text in the h2 tag doesn't have to be a lot bigger than the surrounding body text to give it additional importance.