Dreamweaver MX help! Please!

i need help trying to keep my pop up to ALWAYS stay on the front of a page.

EX: i have 2 thumbnails…when clicked on thumbnail 1 the pop up appears above the the page. when clicked on thumbnail 2 the pop up loads in that same pop up window, but then hides behide the page.

how do i get that ish to stay in the front of a page at each click of a thumbnail?

can anyone help me please?!