Enable backspace in firefox
With the release of Firefox 2.0.x , the backapce button has ceased to act as back button , instead the developers made it to be used as pageup.But no tensions, recently I cam across the following funda on a firefox forum,hope this helps you to reclaim back backspace button as a back button.
Open your firefox browser and type the following code into the address bar:about:config
After that in the filter type:browser.backspace_action
and change it's value to "0" from "1".
For the more curious ones please check out the following link
For Seamonkey as well the same method would be applicable.