If your antivirus warned you, your computer is safe, the anti-virus took care of it. Make sure you update the virus signature file often to keep it up to date. There is an addon for firefox called NoScript. I advise people to install it and give permission only to trusted sites. Even then start with temporarily give permission. Javascript exploit is not a rare occurrence. Read about it here:
http://noscript.net/ then click on get it. You'll need to restart Firefox after the install is done.
Also in the Firefox preferences, don't allow third parties cookies. Don't allow popups. If you go on a site and you want the popup, you give this site only permission. Firefox will ask you.
Hope this helps.
