Bits of .NET

<script type="text/javascript">
        function checklength(i) {
            'use strict';
            if (i < 10) {
                i = "0" + i;
            }
            return i;
        }

        var minutes, seconds, count, counter, timer;
        count = 301; //seconds
        counter = setInterval(timer, 1000);

        function timer() {
            'use strict';
            count = count - 1;
            minutes = checklength(Math.floor(count / 60));
            seconds = checklength(count - minutes * 60);
            if (count < 0) {
                clearInterval(counter);
                return;
            }
            document.getElementById("timer").innerHTML = 'Next refresh in ' + minutes + ':' + seconds + ' ';
            if (count === 0) {
                location.reload();
            }
        }
</script>

<span id="timer">

Reference