pop up window behavior

can someone please tell me why this code in home page does not result in the pop up specified (going_green.html exists with text in it!):

<a href="#" onClick="selectPopUpWindow('going_green.htm');MM_openBrWindow('going_green.htm','gg','width=350,height=350')">We're Going Green

i did not do anything else (ie: specify any attributes)

even after enabling pop-ups it is does not appear (i also added code in body to close it when home page is  reopened although seems pointless right now!)

know this is a lame problem but it is what it is - thanks. dm