function popCalc(url,popW,popH){
//var w = 480, h = 340;

w = screen.width;
h = screen.height;

var leftPos = Math.round((w-popW)/2); 
var topPos = Math.round((h-popH)/2);

var id=Math.floor(Math.random()*10000);

pops=window.open(url,id,'scrollbars=yes,resizable=0,width=' + popW + ',height=' + popH + ',top=' + topPos + ',left=' + leftPos);

if (pops.opener == null)
 pops.opener = self;

};