I stole these instructions from one of my groups:
1.Go to this folder: "C:\Program Files (x86)\Steam\resource\styles" and find the file that says "steam.styles"
2. Open it with notepad or notepad++
3. Scroll down to the comment: "// styles for text used in RichText controls in various places"
4. Where it says "friends_chat_text" all the way to "friends_chat_securitylink", just replace all the instances of "font-size=16" with "font-size=14"
5. Save the file and close it, then restart steam.
Just putting these here just in case.
