function shownav(k,h){
   for(var i=0;i<4;i++){document.getElementById("main_"+k+i).style.display="none";}
   for(var i=0;i<4;i++){document.getElementById("navtitle_"+k+i).className="divnavA";}
   document.getElementById("navtitle_"+k+h).className="divnavB";
   document.getElementById("main_"+k+h).style.display="block";
}