While its certainly not a huge issue with a number of work arounds available through a bunch of different apps these days, lack of true full screen browsing on Mac OS X for a long time has been a common complaint from new and old users alike. This is especially as each version of the most prominent browsers come and go without implementing the feature, that to Windows users, is something that is primitive to say the least.
Luckily in the latest version of Firefox 3.6, the feature has been implemented with the same native feel as their Window’s counterpart. Simply go to View » Full Screen. To exit full screen mode, hit Shift, Command- F.
There are also rumors that many of the multiple monitor support issues present with Firefox on Mac OS X in the past have been worked out. Keep checking BlogsDNA.com for the latest on everything Firefox and Mac OS X related.