No one can help you without more information.
What iOS level are you using?
Does your iPad connect to other WiFi networks?
What make, model, and version WiFi router do you have?
Does your WiFi router have up to date firmware from the manufacturer installed?
How do you have your router configured? Security type (WEP, WPA, WPA, none), MAC filtering turned On? Maximum number of connections set? Etc.
Have you looked at any Apple troubleshooting documents? See http://www.apple.com/support/ipad/wifi/