There are a few things to try:
Reset iPad and router:
Press and hold Home and Power button of the iPad until the Apple logo appears, then release both and let the device power up. This won't remove data or settings.
Turn off the router, unplug it, wait for a few minutes, plug it in and start it again.
Restart both - turn off the iPad, the router and turn them on again.
Make sure that router and iPad are up to date. The latest software for an iPad 3 is iOS 7.1.2.
Get closer to the router, maybe the iPad is too far away.
Remove other devices that are connected to the router.
Maybe you'll need to change the channel on your router.