As the topic says, I'm questioning whether or not its possible for me to find out what page someone's viewing in their browser. What would this be useful for? Well, I'd use it for the who verb. Every time someone logs in or out, I'd check everyones browser, (a HTML based thingy)and if they're viewing the who page, it'd automatically refresh. That way, I don't pull anyone away from what they're doing if they aren't viewing the who list.
You'd have to use javascript to grab the page information.
In response to Nadrew
Ah. Javascript. Not a strongpoint.