Image-mapped header with leaderboard ad in header right widget

I have created an image-mapped header and added it to my site in a header hook. Now my leaderboard ad (which is in the header right widget area) floats above the header instead of overlapping the empty area I created just for the ad in my header. Is there a way to get the ad to overlap my image map? This worked perfectly when my image was not an image map.

Here is my site

Thank you in advance!