Can i limit web-browsing on firefox/safari?

try lookin around parential controls in system prefs

 

try leechblock for firefox

its excellent, very customisable.
https://addons.mozilla.org/en-US/firefox/addon/leechblock/

 

Gah I know the feeling! (Hence why I am on mac rumors instead of reading my game engine architecture book). I've thought about trying to block the internet from the router level and randomly changing my password to the router so that if I want to break my internet rules I have to redo my network, (which means re-adding my printer to the network which is insanely difficult.) That alone would keep me from re-doing my network.

The problem is is that I have to constantly look up documentation and such so I need the internet for school : / Oh, and right now I am an online student so thats a factor too.