how to create a remeber me tickbox on sign in of user

[eluser]dhananjay[/eluser]
when user make login

i m checking if he has checked remember me checkbox
if he has checked i m generating a hash and setting it in his browser
no when any visit login page i am checking for that cookie if cookie has been set i m geeting that hash code if matched makin that user login

now i want to ask how two users can use remeber me from same browser?

if cookie has been set as he move to that login page he is made logged in....