Hi and welcome to the Forum!
Did you read this thread at all? There was info available earlier so I'll just copy it here. I don't know if you have an ipad1 or not, but this type of issue does occur more frequently on this iPad. With the new update to IOS 5.1 members are reporting they are not having this issue any more or not as frequently.
Yes this is an issue that quite a few members are experiencing. The ipad1 has only 256 mb of ram compared to the ipad2 with 512 mb. The best thing to do here is close all your apps completely regularly and clear out history and cookies from Safari, also keep location services to a minimum. From the home screen do the four finger swipe up or double press the home button to reveal your multi task bar. These are all the apps that you have opened at one time. Long press an app until it jiggles and a red minus sign will appear above it. Press the minus sign, this will close the app, not delete it, clear all these apps as this will clear up more ram.
To clear your history and cookies go to Settings - Safari clear history and cookies
This should stop the problem occurring but it's a good idea to close your apps regularly to avoid it. Let us know how you go.