Hi guys ! I have a minor but recurrent and annoying problem with my macbook. Nobody could help me on the French MacForum.

Some URL I visit automatically display what I call a "warning tab" (see pic below). Those "warning tabs" are sometimes designed for 15'' screens, and are very long. So long that the "close" or "cancel" switch is impossible to reach !!! Then, the only thing I can do, as far as I know, is to force Firefox quitting, and obviously I'm losing all my information.

Oh, I use Firefox, and I want to keep using Firefox. So :
1) Do you know what is the geeky term for what I call "warning tab" ?
2) If you also experience that problem, do you know a basic thing I could do (settings for FF or manip'?).

The pic :

That's all folks ! Many thanks !