I am aware of the fact that probably 90% of you must already know about Swiftfox so this post is for the other 10% of WebUpd8 readers. I wrote about how to fix full-screen flash in Firefox and Swiftfox but I never mentioned what Swiftfox is.
By default, Firefox (or Swiftfox) crashes when trying to view a full-screen video on say... YouTube. At least for me it used to crash until I found a fix and from what I've understand it's got something to do with the graphic card drivers and it's affecting both nVidia and ATI. If that is the case for you also, you may want to read on.