Please refer the following URL
I implemeted in the same way as mentioned in following URL
http://bytes.com/topic/c-sharp/answers/253086-pageload-when-back-clicked
i added
<%@ OutputCache Location="None" %>
to my aspx page.
after adding this the page load event is getting fired in IE but not in firefox.

Any help will be higly appreciated.

Thanks
Rupes...