Not hard. You just create a <DIV> with absolute position and display:none
Then use JS
code to place it where you want and change display to block.
I use the technique with my "POPON Calendar" that you can see here:
I also use basically the same technique here:
When you click on one of the artist's names (toward the bottom, e.g., "Dennis Bishop") it pops on a similar DIV.
Even the little guy at the top of the page (just stay at the top for 20 seconds or so) is done using basically the same technique.