Basically, this occurs when the iPad is running low on RAM memory. What it does is that it doesn't store the entire page in its cache, but rather just a preview - so that when you tab back to it, it will reload the page. The suggested solution is to close all the other concurrent pages/apps which you don't require.
iCab has just updateted this morning and one of the upgrades is offline cacheing. Haven't tried it yet.
Also played with Browser+ yesterday which runs pages full screen without a navbar. Control is by swipeing. Navbar is a popup swipe from below with kbd.
So many browsers out there you'd think we'd find the perfect one easily......