js关闭窗口兼容firefox、chrome、ie

function windowclose() {
var browserName = navigator.appName;
if (browserName=="Netscape") {
window.open('', '_self', '');
window.close();
}
else {
if (browserName == "Microsoft Internet Explorer"){
window.opener = "whocares";
window.opener = null;
window.open('', '_top');
window.close();
}
}
}