You cannot use Function keys like F11 as they are used by browser. F11 makes the browser Fullscreen. You can use other keys like ENTER
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
<title>Untitled Page</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1/jquery.min.js"></script>
<script type = "text/javascript">
$(document).keyup(function (e) {
var keyCode = e.keyCode ? e.keyCode : e.which
if (keyCode == 13) {
window.open("http://aspsnippets.com/");
}
});
</script>
</head>
<body>
<form id="form1" runat="server">
Press enter to open webform.
</form>
</body>
</html>
Demo