I downloaded update 7.1 yesterday and have been unable to get online with my wifi since. I am now on my windows desktop - in desperation.
Hi and welcome to the Forum!
Did you do a restart or reset after the update? Always a good idea.
Restart - Press and hold the power off button, the one at the top right. You will see a slide appear to power off, slide this and the screen will go dark and a Whirly will appear. When the Whirly disappears your iPad is now off. Press the power button again until the Apple logo appears, this will take a few seconds and your iPad will restart. You should restart your iPad occasionally also as it will keep it running well. Now see if it is operating.
Reset - Hold the power off button and the home button simultaneously, keep holding them in and you may see the power off slide appear and disappear, wait until you see the Apple logo appear before releasing the buttons. It will take a little longer for your iPad to start.
If those steps don't fix it have a look here, in particular Twerppoet's great post
http://www.ipadforums.net/ipad-general-discussions/118558-dropping-wi-fi-connection.html
Check to see if there are any updates for your router also.