Okay now this description was pretty vague but it could be a few things. First thing to try. Turn wifi off and then one again and try to connect. If this fails read on.
The second step is to select that network in the wifi settings so you get an expanded menu of it. Follow these steps from the home menu on your ipad... SETTINGS>Wi-FI>NETWORK NAME (you have to click the little blue arrow)> FORGET THIS NETWORK. Then turn wifi off and then on. Then try to connect again. If this fails... well read on,
Okay, so now you really know it's most likely not your ipad, so go on down to your wifi router and turn it off, wait ten seconds, turn it on again. WITH YOUR IPAD OFF. Then turn on your ipad on and then try to connect again. If this fails... Then you'll have to do some more complex things. You could try setting up the network again. IF that fails too. Leave some details about your router, brand, year etc... And I'll try to let you know what else it could be.