var w = 480, h = 340;
if (document.all || document.layers) {
	w = screen.availWidth;
	h = screen.availHeight;	
}
var popW = 1000;
var popH = 600;
var leftPos = (w-popW)/2;
var topPos = (h-popH)/2;

function extPop(extLink){
	var popup=window.open(extLink,'a','toolbar=yes,location=yes,directories=no,status=yes,menubar=yes,scrollbars=yes,resizable=yes,width=' + popW + ',height=' + popH + ',top=' + topPos + ',left=' + leftPos );
	popup.focus();
}