Here is a nice walk-through for those who like to view web pages and chat with his buddies on Steam while playing Battlefield Heroes.
Before you can run the Steam Community Overlay in Battlefield Heroes, which is currently still in beta as of 2-16-09, you will need to install 3 pieces of software:
1. Mozilla Firefox
3. Battlefield Heroes
Click the links above to acquire.
This instructable is courtesy of http://ruckman.net