function keyTrap(e)	
{		
  // Netscape uses e, IE window.event		
  var event = (e)?e:window.event;		
  var keyPressed = (e)?e.which:window.event.keyCode;			
  var ctrlPressed = (e)?(e.ctrlKey):window.event.ctrlKey;		
  //var altPressed = (e)?(e.altKey):window.event.altKey;
  
  if (!event.srcElement) event.srcElement = event.target;  
  		
  if(keyPressed==8) //disable backspace button to back history
  {
  	if (event.srcElement.tagName.toUpperCase()=='INPUT' &&         
  	    event.srcElement.type.toUpperCase()!='TEXTAREA' && 
  	    event.srcElement.type.toUpperCase()!='TEXT' &&
   	    event.srcElement.type.toUpperCase()!='PASSWORD')
  	{
      window.event.keyCode = 0;	
      return false;			      
  	}
    if (!(event.srcElement.tagName.toUpperCase()== 'INPUT' && !event.srcElement.readOnly) && 
        event.srcElement.tagName.toUpperCase() !='TEXTAREA' && 
        event.srcElement.tagName.toUpperCase() !='TEXT')
    {
      window.event.keyCode = 0;	
      return false;			      
    }
  }
  
//  if (altPressed)
 // {
  //	alert(alt_message);
  //  //alert("'Alt' key is disabled!"+"\n"+"\u4e0d\u53ef\u4f7f\u7528 'Alt' \u9375!"+"\n"+"\u4e0d\u53ef\u4f7f\u7528 'Alt' \u952e!") ;
  //  window.event.keyCode = 0;	
  //  return false ;
 // }
  
  if (ctrlPressed)		
  {			
    switch (keyPressed)			
    {				
      case 76:	// CTRL-L.					      
      case 72:	// CTRL-H.					
      case 66:	// CTRL-B.					
      case 73:	// CTRL-I.					      
      case 79:	// CTRL-O.					
      case 87:	// CTRL-W.					
      case 82:	// CTRL-R.					
      case 80:	// CTRL-P.					
      case 78:	// CTRL-N.					
      case 112: // CTRL-F1
      case 113: // CTRL-F2
      case 114: // CTRL-F3
      case 115: // CTRL-F4     
      case 116: // CTRL-F5     
      case 117: // CTRL-F6     
      case 118: // CTRL-F7     
      case 119: // CTRL-F8     
      case 120: // CTRL-F9     
      case 121: // CTRL-F10     
      case 122: // CTRL-F11     
      case 123: // CTRL-F12                                                
        window.event.keyCode = 0;	
        return false;			
    }		
  }
  else
  {
    if(keyPressed>=112 && keyPressed<=123)
    {
      window.event.keyCode = 0;	
      return false;			
    }    
  }
}	

if(document.layers)	
{				
  //NS4+		document.captureEvents(Event.ONKEYDOWN);	
}	
document.onkeydown=keyTrap;

//showtips
if (!document.layers&&!document.all){
	event="test"
}