How to disable the back functionality of the browser after we log out

*hello friends,

in my project after logged out when the user hits back button he is
redirected to previous page but when i click or any event is occured
then
page is redirected to login page using before filter, but i need to
restrict
the user to view only login page before logged in. Since i included lot
of
script files this particular code in onload function is loaded after a
few
seconds only.

history.forward();

can anyone help me to fix this issue*

Regards

Mahesh