Code:

<script type="text/jscript">
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    var count=6;
    function countdown(){
        count--; 
        if (count>0){
            Id = window.setTimeout("countdown()",1000);
            var Counter=document.getElementById("counter");
            Counter.innerHTML=count;
        }
        else{
            var Counter=document.getElementById("counter");            
            Counter.innerHTML="0";
            ShowLink();
            window.clearTimeout(Id);
        }
    }
 // -->
</script>