Why doesnt my Iphone wifi work?

Sounds like you need to contact your Internet Service Provider. If your phone will connect to every network but your own, then it's probably your network.

Also, is your internet password protected?

its not hardware issue its possibleyour network name is common like dlink404 try resetting your network settings on the iphone by goping to settings >general >reset >reset netowrk settings . if that didnt work try changing the netork name to unique one like "hill family" , that will improve your connectivity , you might have to contact the manufacturer of your router to perform factory reset on the router and set a new network name ,

try resetting the router find the reset button on the router , push it and hold for 15 seconds untill you see the lights flashed , more likely your router is filtering the mac id of some devices and only letting some device to connect ... resetting will really help .

Have you tried ALL of the steps in this article: http://support.apple.com/kb/TS1398 ?

if TS1398 didnt work and reseting the router didnt work , restore the iphone.

So you've updated your wi-fi router's firmware?

What's the make & model of your router, and what is the current firmware version on that router?

Try making your network an open network temporarily, if didnt connect restore the iphone .if its still didnt connect try doing a dfu mode restore .do not restore from a back up .remember that power cycling the router is different from resetting the router .