function popup(element, width, height)
{
 url = element.getAttribute ? element.getAttribute('href') : element;

 width = Math.min(screen.availWidth, width);
 height = Math.min(screen.availHeight, height);
 
 pos_x = Math.round((screen.availWidth - width) / 2);
 pos_y = Math.round((screen.availHeight - height) / 4);

 return window.open(url, '_blank', 'width=' + width + ', height=' + height + ', left=' + pos_x + ', top=' + pos_y + ', resizable=0, scrollbars=0');
}