login/session advice

hi there

when i build a login system, i usually use login by checking a users table, and then save the info in a cookie, which is time-defined.

I am looking for a better more secure way to do this, which could include more advanced features, such as:
1) checking that the users isnt logged in twice at the same time
2) that the 'session' does not remain live if the browser window is closed
3) more secure - doesnt mean saving user info in session (?)

can anyone suggest anything?

thanks!

Classic ASP, but for now I'm just inquiring in the theory

You could adapt the concept of this tutorial 15daysofjquery.com/safer-contact-forms-without-captchas/11/ to your situation