how do u play on the web with your ps2 like what do i need to buy?

Question

i dont know how to do it or what will i need

Answer 1

It's hard to find these now, but you'll need this thing:
http://www.amazon.co.uk/Sony-Computer-Entertainment-UK-Network/dp/B00003E37F
It's necessary only if you have old PS2 (the fat one). The slim one has a RJ-45 Ethernet connector. Not too many PS2 games support online.

Answer 2

PS2? You technically can't. You'd need to hook your PS2 up to a PC and try to download this program (the name escapes me but it's basically a homebrew browser) that allows your PS2 to be used as a normal PC. I don't recommend this honestly.
Now, to play a few of the online games, you simply need a PS2 (must be one of the original ones sold before 2003 - not a PS2 Slim), the PS2 network/ethernet adapter and the PS2 Hard Drive. All three of these things are sold separately.
If by chance you meant PS3, then everything comes in the box. Simply plug and play.
I think japanese gamers got a littler more and were able to use their PS2 as a browser and surf the web. I could be wrong on that though.