Hi Sreenivas,
The pages are retrieved from browser cache when you click the back button of the browser. If you are not submitting data from page1 to page2, the version from the browser cache is OK.
However if there is information you submitted in a form. As a security precaution, Internet Explorer does not automatically resubmit your information for you if Back button has been pressed. And you will get "Warning: Page has Expired ".
To resubmit your information and view this Web page, please click the Refresh button.
BTW, I guess you might refer to KB arctiles which apply to ealier versions of IE, e.g. the following KB is for IE 4. If so, please ignore it.