var win=null;
function popup(mylink, windowname)
{
if (! window.focus)return true;
var href;
if (typeof(mylink) == 'string')
href=mylink;
else
href=mylink.href;

//get image real size
var img = new Image();
img.src = href;

if (win) win.close();
win=window.open(href, windowname, 'width='+(img.width+50)+',height='+(img.height+50));
return false;
}