Help! I opened a bookmark in iOS 7 and my device locked up!

I was on iOS 7 yesterday and opened a bookmark (App Bounty). The screen was white while the web page loaded, but I noticed that it was taking longer than usual to load. I pressed the home button, but it wouldn't close the bookmark. Then I pressed the power button, and the screen went off, as usual. But when I pressed the power button, it wouldn't come back on! I left it for a while, but I still couldn't get it to come on. Then I noticed - the iPad was still on. My email notification tune went off, and I can take screenshots. I tried plugging it into my PC, but iTunes said it needed to upgrade to iTunes 11, which I can't do at the minute.

Does anybody have any suggestions? I'm on an iPad 2 16GB running iOS 7.0.