Firefox covering up gnome panel at top of screen

[singlecell]

> I had this issue several weeks ago - I resolved it by making a change to
> one of the Compiz settings - don't recall which precise setting it was,
> nor can I check unfortunately.
> 
> 
> 

I also had the same issue, and found the answer in the internet...

The fix was to disable (un-check) the setting "Legacy Fullscreen 
Support" in the "workaround" section of compizConfig.

Hope the fix works for you.