I found getting the game to start off well quite tricky. Here's what I ended up with. The key idea is to start off with a reasonable set of 5 cards - i.e. not all different. What will be new for you is my j loop which counts backwards.

  ...
  <script>
    var g_cards=[];
    for (var i=0;i<5;i++) g_cards.push(Random(52));
    for (var i=0;i<5;i++) {
      pick0();
      for (var j=4; j>0; j--) {
        g_cards[j]=g_cards[j-1];
      }
    }
    for (var i=0;i<5;i++) {
      var image=document.getElementById(i);
      image.src='cards/'+g_cards[i]+'.png';
    }
  </script>
</body>
</html>