detecting a browser's back button
I'm sorry, I know (or think) this question is answered already on the board in a couple places - but I'm still new and I just can't wrap my head around this.
I have a jquery-powered "start page" that checks your log in and if successfull it slides in a "menu" of new places to go. The problem is, if you click back from one of the new places, the original "start page" looks as if you never logged in. You have to reload the page. Not very intuitive and this website is for kids. Now I've tried setting form field values with server session variables, javascript variables, etc etc but they all get reset when you click back. I've tried the "onunload hack" which I don't fully understand, and then read a bit about the onhashchange event which is from what I gather only compatible with HTML5 browsers...
So... is there no way to detect if the user is already logged in when they click the back button or am I not doing enough homework?
Thanks all for any help/insight you could provide...