[melky]

<script>
var store = {
     open : function(){
          if("sessionStorage" in window)
               return sessionStorage.getItem('count');
          else 
               return /count=([^;]+);/.exec(document.cookie)[1];
     },
     save : function(value){
          if("sessionStorage" in window)
               sessionStorage.setItem('count', value);
          else
               document.cookie = "count=" + value;          
     }
};

var count = store.open();
count = count && isFinite(count) ? parseInt(count):0;

document.write('Вы посетитель № '+count);

count += 1;
store.save(count);
</script>