Yes, the session exists on the server. I don't know if requesting a html page would reset the timeout, but I'd suspect it would. Either way, going between them will not erase the session automatically, even if it does cause issues with a timeout. Your best bet is to test it. Set something up in the session. Refresh a html page every minute or so for 10 or 15 minutes, whatever the timeout is, plus a bit. Then go to a page that shows the session value.
Christian Graus Driven to the arms of OSX by Vista. Read my blog to find out how I've worked around bugs in Microsoft tools and frameworks.