Try rebooting your router and or cable modem. Unplug it/them for about 30 seconds and then plug back in. See if it works then. Reboot your iPad as well.
Reboot the iPad by holding down on the sleep and home buttons at the same time for about 10-15 seconds until the Apple Logo appears - ignore the red slider if it appears on the screen - let go of the buttons. Let the iPad start up.