javascript + atlas problem

[24sharon]

I have a javascript code to stop the backspace to go 'BACK'

my code:

 <script type="text/javascript">
   
         if (typeof window.event == 'undefined'){
        
           document.onkeypress = function(e){
            var test_var=e.target.nodeName.toUpperCase();
            if (e.target.type) var test_type=e.target.type.toUpperCase();
            if ((test_var == 'INPUT' && test_type == 'TEXT') || test_var == 'TEXTAREA'){
              return e.keyCode;
            }else if (e.keyCode == 8){
              e.preventDefault();
            }
           }
         }else{
       
            document.onkeydown = function(){
            var test_var=event.srcElement.tagName.toUpperCase();
            if (event.srcElement.type) var test_type=event.srcElement.type.toUpperCase();
            if ((test_var == 'INPUT' && test_type == 'TEXT') || test_var == 'TEXTAREA'){
              return event.keyCode;
             }else if (event.keyCode == 8){
              event.returnValue=false;
              }
           }
         }
    </script>

when I add this code to a page use atlas the atlas dont work.

what the problem?
or there is any way to fix it.

thanks!