document.onkeydown = function(){
if(window.event && window.event.keyCode == 112) 
        { // Capture and remap F1
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 113) 
        { // Capture and remap F2
     window.event.keyCode = 505;
       }
	   
if(window.event && window.event.keyCode == 114) 
        { // Capture and remap F3
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 115) 
        { // Capture and remap F4
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 116) 
        { // Capture and remap F5
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 117) 
        { // Capture and remap F6
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 118) 
        { // Capture and remap F7
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 119) 
        { // Capture and remap F8
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 120) 
        { // Capture and remap F9
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 121) 
        { // Capture and remap F10
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 122) 
        { // Capture and remap F11
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 123) 
        { // Capture and remap F12
     window.event.keyCode = 505;
       }
if(window.event && window.event.keyCode == 505) 
        { // New action for F3
     alert('Tecla no disponible');
     return false; 
        // Must return false or the browser will refresh anyway
     }
}


function handlePress(e) {
  var AshiftPressed = (window.Event) ? e.modifiers & Event.SHIFT_MASK : e.shiftKey;
  var ctrlPressed = (window.Event) ? e.modifiers & Event.CONTROL_MASK : e.ctrlKey;
  var altPressed = (window.Event) ? e.modifiers & Event.ALT_MASK : e.altKey;
  
  if (shiftPressed) {
    alert("La tecla Shift esta deshabilitada en esta página");
	e.cancelBubble = true;
	return false;
  }  
  if (ctrlPressed) {
  	alert("La tecla Control esta deshabilitada en esta página");
	e.cancelBubble = true;
	return false;
  }
  if (altPressed) {
  	alert("La tecla Alt esta deshabilitada en esta página");
	e.cancelBubble = true;
	return false;
  }
  else return true;
}