Full-screen mode has traditionally been missing from Mac browsers. Safari and Firefox still don't have it, but Chrome does.

Firefox does. Safari still doesn't.

Oh, sorry about that, my Firefox is slightly out of date (3.5.9) and doesn't seem to have full-screen mode.

Doesn't 3.5.9 have a security hole?

I think 3.5.8 had an exploitable use-after-free bug, but 3.5.9 fixed it.

Use Megazoomer to make any app full screen:

http://www.macupdate.com/info.php/id/21275/megazoomer

Yes, in Chrome, just hit Command-Shift-F for full-screen. It's awesome!

Btw, this PlainView app appears to be 2 years old. How is this getting upvoted?

There are also plugins for Safari that add it such as Saft.

Yeah. The developers at barbarian mentioned in a blog post that they started the project since they needed a browser with fullscreen support for mac to present slides. But I personally use this to browse things where I need concentration - like reading some serious stuff.

And there is a "Kiosk mode" which would prevent me from doing an alt+tab. To come out of kiosk mode I would have to type my password once. When the password prompt comes up I would ask myself once if I need to really go to some other app now, or if I should continue concentrating on reading this for more time. This process makes me concentrate longer on what I'm reading.