Is it true that if you don't log off from a site, you leave certain ports open allowing access to your 'puter?

My bank’s website specifically warns you to not only log out, but to close the browser window due to possible security breaches. I always assumed it meant someone might access your records on that site, not necessarily on your entire computer. Because of that assumption, I’ve only ever worried about it on sites with sensitive personal data on them (financial, medical, etc.). Perhaps I’m wrong?

Logging onto a website has nothing to do with opening new ports on your computer and keeping connections open so if you stay logged onto a website you’re okay with respect to that. The only reason I can think of off the top of my head for logging out of a website once you’ve finished on it is that if anyone else has access to that computer (or say, for example, if your laptop got stolen) then they’d be able to access that site with your account automatically logged in. So you shouldn’t worry about it, they were either pulling your leg or had been misinformed themselves!

I would like to add however that connections and ports are involved when browsing websites and such, but the specific action of staying logged in isn’t directly linked to leaving ports and connections open. You need to create these connections and for certain ports to be open on your computer and the server just so you can access the information on the server!

Sometimes yes. Sometimes no. Calculate your strategy.

I try to leave my computer in standby sometimes and it wakes me up in the middle of the night because my mIRC program or Yahoo IM or something else starts up from another end. That is startling and a little disturbing.