Originally Posted by ReSpawN

That should work fine. Since you're not setting any content on the cookie and the timer in negative, it's automatically a false cookie. Plus, almost every browser including Netscape and Internet Explorer delete out-of-date cookies. Otherwise, it's not a problem since you can make your system check for cookies and them validate the timestamp given.

To sum it up once again, that should work fine. And oh yeah, to the quote. Think of setting (and unsetten) of cookies as headers. It's basically the same rule, before ANY output. I haven't found a good method to unset it in-script, but I do it with a post variable.