Weird Thing about PR

I just noticed the weirdest thing happening to the PR of a webpage.
Here's what happens: I'm on a pr6 page, all looking good. But When I add a random GET variable (?a) at the end of the url and hit enter the same page shows up, but the pr is 0.
It makes sense for this to happen but it's still weird since the page is still the same. And for example if you add just a question mark (?) nothing happens to the pr.

Totally off-beat post. There's no point I was trying to make. I just thought I'd pop in a message 'cause I like weird things.

Because the urls are different. If there was a script in place you would be able to display a different page.

Same thing with http and www pages.

Its like logging into BHW with a different username. It will still be you but there would be no such username in the database.