The default behavior of a backspace key is (by default) annoying on forms in both IE and minimally in Firefox and some others.
When you are in a text box or text area the back space key functions appropriately in all browsers that I have seen to this point. When you have a select pulled down or in focus, then one of the more annoying features of the backspace key shows up. When in this scenario, your user goes back to the previous page, and this I consider an annoying feature, particularly because data entry usually use the keyboard to...