I use safari and I can't sign out of my account. I am not the only one using this pc and I desperately need to sign out. I went as far as to try to delete my account, but I can't even do that.
PLs I need to sign out ASAP.
You don't mention what site you're trying to sign out of, which would help quite a bit. I'd just recommend that you close your browser (Safari), which should end your session. If you launch Safari again and are still signed in, then they are probably maintaining your login with a cookie.
In this case, launch Safari, hit control-comma, go to the security tab, hit the "Show Cookies" button, and then either remove the cookie for the site you're logged into, or just remove all cookies. That should end your session.