function addListener( a, b, c, d ) {
    if( a.addEventListener ) {
      a.addEventListener( b, c, d );
      return true;
    } else if( a.attachEvent ) {
      var e = a.attachEvent("on"+b, c );
      return e;
    } else {
      alert("Handler could not be attached");
      return false;
    }
  }

  function bind( a, b, c, d ) {
    return window.addListener( a, b, function() { d.apply( c, arguments ) } );
  }

  function handleKeystroke( evt ) {
    //alert( evt.keyCode );
    // Grab the cross browser event
    if( !evt ) evt = window.event;
    // Character code of key pressed
    var asc = !evt.keyCode ? ( !evt.which ? evt.charCode : evt.which ) : evt.keyCode;
    // ASCII character of above code
    var chr = String.fromCharCode( asc ).toLowerCase();
    for( var i in this ) {
      if( asc == i ) {
        this[i](evt);
        break;
      }
    }
  }

  function cancelEvent( evt ) {
    evt.cancelBubble = true;
    evt.returnValue = false;
    if( evt.preventDefault )
      evt.preventDefault();
    if( evt.stopPropagation )
      evt.stopPropagation();
    return false;
  }

  // KEY COMMANDS
  var keyMap = new Array();
  var ARROW_LEFT    = 37;
  var ARROW_RIGHT   = 39;
  keyMap[ARROW_LEFT] = arrowLeft;
  keyMap[ARROW_RIGHT] = arrowRight;

  function arrowLeft( evt ) {
    if(document.getElementById('imgPrev')) {
      document.location=document.getElementById('imgPrev').href;
    }
    cancelEvent( evt );
  }
  
  function arrowRight( evt ) {
    if(document.getElementById('imgNext')) {
      document.location=document.getElementById('imgNext').href;
    }
    cancelEvent( evt );
  }
  
  // Add the keydown listner to the document object for global capture
  bind( document, 'keydown', keyMap, handleKeystroke );