1. Do not use "pt" in your fonts. Different browsers view these very differently and you will not have much control over that. And avoid using inline styles when possible. Put them in your style sheet.
2. In your style sheet (after removing the inline style references), add something like this:
#comments-post #author {font-size:90%; color: red}
#comments-post #email {font-size:90%; color: blue}
#comments-post #url {font-size:90%; color: green}
The different colors will "tell" you if the font has been changed and the style references are right. You might have to play with this a little to get the right order of style references right.
Once you get the font size set right, and all the other details, get rid of the color references.
3. I also recommend you spend some time in the WordPress Codex, documentation site, at http://codex.wordpress.org, especially with articles like:
Finding Your CSS Styles
WordPress Blog Design and Layout
Template Files
Stepping Into Template Tags
4. A reminder, this forum is run by volunteers, and they are simple but eager folks who want to help. Not everyone knows everything. We like to solve one problem per post, not every problem. We also like to be treated nicely, thanked on occassion, and forgiven for slipping up once in a while.