My computer and internet?

my internet will attempt to open and fail when i try to open something or do a Google search but if i hit reload it will just come up normally. however it will go on spree's where nothing works i cant open anything normally on a specific site like yahoo answers i couldn't write a question or look at any questions i had to use another PC. its not the int speed cuz my dads is fine and converges fast and its not the browser(firefox) as internet explorer is worse than ff so what is it it?? it is extremely frustrating