You dont know & cant know.
You can record when a visitor requests a page, but there is no way of know
if the person is still on that page or whether they have moved on to a
different site.
By recording visitors to a page, you can of course make some assumptions:
you could assume that any visitor that requested the page withing the last X
minutes is likely still to be there, therefore you would have approximately
Y visitors currently at that page.
You could also make an assumption that if a user request Page1 then 1
minute later they request Page2, they may well no longer be looking at
Page1. Of course, the user may have multiple browser windows open...
hth
Chris
