Does jailbreaking an iphone ruin the warranty?

I'm thinking about jailbreaking my iphone 4s, i pay for a warranty $10 a month from ATT (if my phone breaks basically), so say I got water damage and it doesn't turn on or if i shatter the screen and it just doesn't work. Will it ruin the warranty? Or is there anyway to take off the jailbreak when your phone does crack or break to get the warranty back?

No. Yes, there's a way, you simply restore it and there's no way for them to tell.

Jialbreaking voids the warranty, however just restore the firmware in itunes and nobody will know it was jb''d

Long story short, yes.

To get rid of it, restore through iTunes

Yes it voids the warranty.

Yes it does, you can of course revert, assuming your phone is in a condition to plug it into itunes