lay = new Array(3);
lay[0]='Layer0';
lay[1]='Layer5';
lay[2]='Layer7';


function showhideLAYER(num){
  for(i=0;i<lay.length;i++){
    if(i==num){
      lay_name=lay[i]
      showLAYER(lay[i]);
      setTimeout('hideLAYER(lay_name)',20000);
    }else{
      hideLAYER(lay[i]);
    }
  }
}
function showLAYER(layName){
  if(document.layers)document.layers[layName].visibility='show';
  if(document.all)document.all(layName).style.visibility='visible';
  if(document.getElementById)document.getElementById(layName).style.visibility = "visible";
}
function hideLAYER(layName){
  if(document.layers)document.layers[layName].visibility='hide';
  if(document.all)document.all(layName).style.visibility='hidden';
  if(document.getElementById)document.getElementById(layName).style.visibility = "hidden";
}