my requirement is after clicking of browser back button  i need to display 

one alert message(are you sure want to leave this page if yes go to previous page or else stay on same page)

Ex: i have login page,menu page again in menu bar i have one dropdown masters  again master has sub dropdowns 1)master1 2)master2 If you try open master2 page it can be redirect to login page for n nof pages i am going to do like that right now i am at master2 page before that i have opened master1 in master2 page after clciking browser back button i need to dipslay confirm message and open previous page(Ex:master1) 2)If the session has been expired (i have been loogef of project) even thought if i press back button at that time it was opening master1 if i can insert any values at that values are inserting i don't need like that