function w_central(a,b,d,t) {

	var br=a;
         var ho=b;
	var h = (screen.availWidth - br) / 2.2;
         var v = (screen.availHeight - ho -100) / 2;
	var datei = d;
         var zeit = t;
	var params = ('width='+ br +',height='+ ho +',left='+ h +',top='+ v);
	var a=window.open(datei,'',params);

	a.setTimeout('window.close()',zeit);
}