function Init(){
         for(var i=1;i<=13;i++){
         document.getElementById('p'+i).getElementsByTagName('img')[0].style.display = "none";
         }
         setTimeout(makeNavi,1000);
}
function makeNavi(){
         var zufall=Math.ceil(Math.random()*13);
         var show;
         if(document.getElementById('p'+zufall).getElementsByTagName('img')[0].style.display=='none')show='block';
         else show='none';
         document.getElementById('p'+zufall).getElementsByTagName('img')[0].style.display = show;
         setTimeout(makeNavi,1000);


}
window.onload = Init;