document.onkeyup = function (Ereignis) {
  if (!Ereignis)
    Ereignis = window.event;
  if (Ereignis.which) {
    Tastencode = Ereignis.which;
  } else if (Ereignis.keyCode) {
    Tastencode = Ereignis.keyCode;
  }
    switch (Tastencode){
      case 37: window.location = document.getElementById('doubleleft').href;
      break;
     
      case 39: window.location = document.getElementById('doubleright').href;
      break;
    }
}