Make pop-up appear over header layer

I use a DHTML pop-up window that shows either text or a video (depending on which link is clicked in the header of my site), but the site header in Catch-Box is using a layer that results in it appearing over the pop-up window that overlaps the header. Where is that controlled and/or how do I make my pop-up be the top-most “window”? You can see this effect by going to my site (www.flobee.net) and clicking the site’s tagline. I have repositioned the pop-up so it is out of the way of the header (depending on the size of the window), so if you drag it up to overlap the header you will see the pop-up’s overlap disappear behind the header panel/frame/span.