<sc ript type="text/javascript">
function preventSelection(element){
  var preventSelection = false;
 
  function addHandler(element, event, handler){
    if (element.attachEvent) 
      element.attachEvent('on' + event, handler);
    else 
      if (element.addEventListener) 
        element.addEventListener(event, handler, false);
  }
  function removeSelection(){
    if (window.getSelection) { window.getSelection().removeAllRanges(); }
    else if (document.selection && document.selection.clear)
      document.selection.clear();
  }
  function killCtrlA(event){
    var event = event || window.event;
    var sender = event.target || event.srcElement;
 
    if (sender.tagName.match(/INPUT|TEXTAREA/i))
      return;
 
    var key = event.keyCode || event.which;
    if (event.ctrlKey && key == 'A'.charCodeAt(0))  // 'A'.charCodeAt(0) можно заменить на 65
    {
      removeSelection();
 
      if (event.preventDefault) 
        event.preventDefault();
      else
        event.returnValue = false;
    }
  }
  addHandler(element, 'mousemove', function(){
    if(preventSelection)
      removeSelection();
  });
  addHandler(element, 'mousedown', function(event){
    var event = event || window.event;
    var sender = event.target || event.srcElement;
    preventSelection = !sender.tagName.match(/INPUT|TEXTAREA/i);
  });
  addHandler(element, 'mouseup', function(){
    if (preventSelection)
      removeSelection();
    preventSelection = false;
  });
  addHandler(element, 'keydown', killCtrlA);
  addHandler(element, 'keyup', killCtrlA);
}
 
preventSelection(document);
</script>