var lastMenuLayer = 0;

function showMenuLayer (pageId) {

     if (lastMenuLayer!=0)
         hideMenuLayer (lastMenuLayer)

     if (document.getElementById && document.getElementById(pageId) != null) {
          document.getElementById(pageId).style.visibility = 'visible';
          document.getElementById(pageId).style.zIndex = 1000;
          lastMenuLayer = pageId;                              
          return lastMenuLayer;
     }
}



function hideMenuLayer (pageId) {

          if (document.getElementById && document.getElementById(pageId) != null) {          
               document.getElementById(pageId).style.visibility = 'hidden';
               document.getElementById(pageId).style.zIndex = 999;
          }
             else
                     document.getElementById(pageId).style.visibility = 'visible'; 
}



function hideLastMenuLayer () {          
         if (lastMenuLayer != 0) {
                document.getElementById(lastMenuLayer).style.visibility = 'hidden'; 
         }
}