Im Develop Online Exam Project In Asp.Net With C#..... And I Set Timer In Test... But When Page Is Refresh Then Timer Are Also Restart... Plz Give Me Some Suggestions...

<script type="text/javascript">
        //for timer...
        var mins
        var secs;
        function cd() {
            mins = 1 * m(document.getElementById("TxtTimer").value);
            secs = 0 + s(":01");
            redo();
        }

        function m(obj) {
            for (var i = 0; i < obj.length; i++) {
                if (obj.substring(i, i + 1) == ":")
                    break;
            }
            return (obj.substring(0, i));
        }

        function s(obj) {
            for (var i = 0; i < obj.length; i++) {
                if (obj.substring(i, i + 1) == ":")
                    break;
            }
            return (obj.substring(i + 1, obj.length));
        }

        function dis(mins, secs) {
            var disp;
            if (mins <= 9) {
                disp = " 0";
            } else {
                disp = " ";
            }
            disp += mins + ":";
            if (secs <= 9) {
                disp += "0" + secs;
            } else {
                disp += secs;
            }
            return (disp);
        }

        function redo() {
            secs--;
            if (secs == -1) {
                secs = 59;
                mins--;
            }
            document.getElementById("TxtTimer").value = dis(mins, secs);
            if ((mins == 0) && (secs == 0)) {
                window.alert("Time is up. Press OK to continue.");
                window.location.href = "MyScoreCards.aspx";
            } else {
                document.getElementById("form1").value = setTimeout("redo()", 1000);
            }
        }

        function init() {
            cd();
        }
        window. önload = init;
    </script>

    <style>
        /* for timer... */
        .timer {
            border: none;
            font-family: verdana;
            font-size: 16pt;
            font-weight: bold;
            border-right-color: #FFFFFF;
        }
    </style>