var tP=0; var eF=0;
function failed() {eF=1}

var popWin = window.open("","ptest","width=1,height=1,left=5000,top=5000",true);
window.onerror=failed
var pW = window.open("","ptest","width=1,height=1");
eF = pW == popWin ? 0 : 1;
popWin.blur(); 
popWin.close(); 
tP = eF == 0 ? 1 : 0;
window.onerror=null;