Now I've worked out how to get the pop-up window to work i now want the pop-up to appear centre screen as apposed to the top left the code on the button is below but what do i need to alter to achieve this.

on (release) { getURL("javascript:window.open('image1.html','imag e1','width=500,height=500,top=0,left=0,toolbar=no, scrollbars=yes,resizable=no,menubar=no,status=yes, directories=no,location=no'); void(0);");
}