Seems like both Firefox and Safari on Mac cannot show the webpage in a full screen mode?

"Saft will do it for Safari. There is a different version for 10.4, 10.5, and 10.6 so be sure to grab the appropriate one.

http://www.macupdate.com/info.php/id/12402/saft"

"It isn't possible to go Full Screen with Firefox on Mac, Safari's probably similar in this case. Although you can maximize Firefox to fit the screen. Create a new bookmark and make this the location:

javascript:self.moveTo(0,0); self.resizeTo(screen.availWidth,screen.availHeight);

clicking it should expand Firefox to fit the screen."