Firefox 4 is a new browser, so you kind of want to stay with other browsers for now. Since it is a new browser, the Mozilla team has not
added all of the tricks and trades yet. They are working on it, but I would stay with another browser until then bud...
I hope this helps, I know it is not a straight forward answer but, soon the capabilities will be compatible, as of of past reference.
Hope This helps, and if it does, Thank me....
Haha, Have Fun
- Will, MML Design
PS: Don't worry, an update will release soon.
For quick Reference: http://support.mozilla.com/en-US/home