Who knows what code causes Firefox to rescroll my pages to the very top of the browser window when reloading the page or hitting the back button?

Say for example you're on my web page... you scroll down a bit, click a link, then click the back button and WHAMO! Firefox scrolls you to the top of the page.

This happens on three of my domains, on two different servers, but only on my PHP pages. My html pages don't rescroll.

/at my wits end