var w = 480, h = 340;

if (document.all || document.layers) {
   w = screen.availWidth;
   h = screen.availHeight;
}else{
	w=screen.width;
	h=screen.height;
}

var url;

var popW;

var popH;

function popUp(url, popW, popH, name){ 
var leftPos = (w-popW)/2, topPos = (h-popH)/2;
window.open(url, name,'width=' + popW + ',height=' + popH + ',top=' + topPos + ',left=' + leftPos + ',scrollbars=no');
}