The statement below does nothing when the Button1 is pressed none of the innerHtml statements are enacted.

<script type="text/javascript">
        function getajax() {
            var xhr;
            if (window.XMLHttpRequest) {
                xhr = new XMLHttpRequest();
            }
            else if (window.ActiveXObject) {
                xhr = new ActiveXObject("Msxml2.XMLHTTP");
                document.getElementById("<%=Label1.ClientID%>").innerHTML  = "Windows";
            }
            else {
                throw new Error("Ajax is not supported by this browser");
                document.getElementById("<%=Label2.ClientID%>").innerHTML = "Ajax is not supported by this browser";
            }
            xhr.onreadystatechange = function () {
                if (xhr.readyState == 4) {
                    if (xhr.status >= 200 && xhr.status < 300) {
                        //executes on success
                        document.getElementById("<%=Label3.ClientID%>").innerHTML = "Success";
                        xhr.open("POST", Default.aspx / GetValue);
                        xhr.send();
                    }
                    else {
                        //executes on error
                        document.getElementById("<%=Label2.ClientID%>").innerHTML = "Error";
                    }
                }
            }
        }
    </script>