A good Spell Checker Extension/plugin for Browsers?

Are there any good spell checker extension/plugins for Firefox or Netscape browsers? (I'll even take a spell checker for IE if I'm desperate.)

I'm reviewing and editing a large number of website content. Right now I've been downloading the file into FrontPage and then doing the spell checking there. Takes a lot of time. Is there a way to do it right on the browser?

I did some googling and saw some extensions by third party vendors, but did not see any on Netscape or Firefox's official website. If you are using a good one please let me know. Thanks!

 

Thanks Mr. MEOWGI, I'll give it a try.