ns = (document.layers)? true:false 
ie = (document.all)? true:false 
sClicked = ""

function showLayer(id) {
 if (ns) document.layers[id].visibility = "show"
    else if (ie) document.all[id].style.visibility = "visible"
}

function hideLayer(id) {
 if (ns) document.layers[id].visibility = "hide"
    else if (ie) document.all[id].style.visibility = "hidden"
}

function clickit(id) {
 if (sClicked == id) {
   hideLayer(id)
   sClicked = ""
 } else {
   if (sClicked!="") hideLayer(sClicked)
   showLayer(id)
   sClicked = id
 }
}