function Tastendruck (Ereignis) {
	if (!Ereignis)
   {
		Ereignis = window.event;
   }
	if (Ereignis.which)
   {
		Tastencode = Ereignis.which;
	}
   else if (Ereignis.keyCode)
   {
		Tastencode = Ereignis.keyCode;
	}

   if(Tastencode == '39')
   {
   	if (document.getElementById("previouspic"))
      {
      	link=document.getElementById("previouspic").href;
         window.location.href=link;
      }
   }
   else if(Tastencode == '37')
   {
   	if (document.getElementById("nextpic"))
      {
      	link=document.getElementById("nextpic").href;
         window.location.href=link;
      }
   }
}

document.onkeydown = Tastendruck;