How can I get autofill to keep my passwords?

How can I keep others from figuring out how to get into my emails here? anything yahoo can do to prevent this?

• a friend of mine set my comp up, he is very nosey and has gotten into my yahoo, through my im that was left up accidently and he got in it when I was at work. Now is there anything yahoo can do to prevent this from happening? if I leave up my im then he can get into my mail without even knowing my password and I just seen where he set me up to have my yahoo open for 2 weeks of mail. With this done he can check my emails from his own home from his own computer, now is there something that can be done so this can't happen again or do I always need to make sure everything is off and it takes so long to boot up on my comp when I come home in morn. He does not know my passwords at all, but with im up he can get into my mail, can you take off the box on my option to keep it open? So if I want to check it I have to get in with my passwords? If he comes in and my im is up, he will go back in and redo the box again, so can yahoo fix it so it won't be a option for me?

• Answer:

  Log off your IM when ever oyu leave your computer. remove the option "remember my usre id and password" and "Sign in Automatically" When ever you want to be on IM login and then log out. Hope you can do atleast this. If not no one can help you.