Why firefox 10.1 uses full screen on Snow Leopard while Chrome and Safari do not? I am new to the Mac World, I am stuck with the fact that on my 15 inch Mac Book Pro only Firefox 10.1 uses all the screen, while Chrome and Safari only use a portion of it. Chrome is the thing I miss most because it's the browser I usually use. 

How do I set it to use the full screen space?

I use Snow Leopard 10.6.8
I love Divvy - it's something that I feel OSX needs and that would allow you to set a shortcut for it. Otherwise the green orb on the top left will take you to full height, and then you can drag out horizontally to your chosen width. 

Alternatively, should you upgrade to Lion, Chrome has a full-screen mode which hides all the other apps.