Here is a div with some links back to on top of this div a transparent PNG has been placed using absolute positioning over the top. You can click on links through the transparent parts of the PNG. This method requires using CSS conditional statements for IE. Should be cross browser compatable (tested with IE, Firefox and Chrome).

Valid HTML 4.01 Strict

The behavior is slightly differnt for IE, only areas where there is transparency in the image can be "clicked through" however in other browsers, the "pointer-events:none;" passes clicks regardless of image/div content.
This DIV is overlayed on top of the yellow DIV and has a transparent png loaded into it.