PUT login arg caching: I've got to be missing something.

Let me try again: I *have* to be missing something.

I have our users log in, passing the userid and password in PUT args.

They then get where they were trying to go, and every page has a  
logout link on it, which I hand to liveUser in the validate script I  
include from every page.

So, if the user logs in, then logs out, then uses the history menu to  
go back to the page immediately after the one they saw after they  
logged in... They just silently log in again.

This can't be right. All these major websites using LiveUser can't  
tolerate this behavior.

It's clear how to fix it myself, but I can't believe there isn't  
something already in LiveUser to deal with this.

What am I missing?

Cheers, and thanks.