It's a RAM limitation issue. When the iPad 'runs out of RAM' the app quits and returns you to the homepage. You can mitigate the effect by completely switching off the iPad by holding down the Power button until the slider control appears then acceptiing the offer to switch off. When the iPad turns off and powers up again, the operating system does a number of 'clean up' operations, one of which is to consolidate all the free RAM, so this will help. But, if the web page is simply too large for Safari to handle (intense graphics, lots of other information etc) then the iPad may simply be unable to handle it.
Tim