How can I make internet windows independant of eachother for multiple users?

(I have Internet Explorer.)

Unfortunately, I live with two other Yahoo account holders and we all use the same friggin' computer! When I sign in to my email and go away for two seconds sometimes someone else will jump on and sign into their account (Mail, Answers, 360), and then when I come back and refresh the page I become them! It is VERY irritating. I have to sign out and back in every time I go to another page so I don't have to X out of their thing (and vice versa).

I have heard there's a way, by changing some settings or something, to make the internet windows totally independant of eachother so that doesn't happen. Please tell me!!!! I'm not too computer literate, so the more detailed the instructions the better. But thanks for any help you can give!