Is there any differences if your text/font is small and tiny? For example: Does webmaster forum have the same backlink value as webmaster forum?
It has no effect, when someone clicks on your link from different site that's going to be a backlink, but it doesn't matter if the font is big or small.
The font size really doesn't matter to the search engine bots. But, sparingly using bold text in some of the keywords does have an impact.
text in an <h1> or <h2> tag is recognized by google as being more important in my opinion. I don't believe that the size that you specify for text in your css makes no difference to google