If you scroll the page, the left column scrolls and the right does not (it has it's own scroll bar, which has nothing to do with the question). So it appears as though the right column is fixed, but it doesn't overlap the left if you resize the browser.
Sorry. I'm not seeing what you describe in either Firefox or IE9.
If you want to give your division its own vertical scroll bar, use CSS height:value along with overflow property.
Demo of overflow property applied to 2 divisions:
Ok, maybe it isn't supported in your browser. What I am seeing is different that the overflow. So if you go to the contact form on your site (http://alt-web.com/contact.shtml) and pretend that there is no header, that the page starts at the line right above the words "contact form". So you have 2 columns the left yellowish one and the right grey "you are here"one. Now pretend that if you scroll the "contact form" side and the browser scrollbar moves (no scrollbar inside of the div). As you scroll the "you are here" grey side doesn't move vertically, like it is fixed. It does move horizontally when you resize the browser ,but it always stay right next to the yellowish column.