var ns4 = (document.layers)? true:false;
var ie4 = (document.all)? true:false;
var ff = (document.getElementById && !document.all) ? true : false;
last='default'		
function showlayer(string) {
  if (last!='default'){
  if (ie4) {lastlayer=eval('document.all.'+last+'.style')}
  if (ns4) {lastlayer=eval('document.'+last)}
  if (ff)  {lastlayer=eval('document.getElementById("'+last+'").style')}
  lastlayer.visibility="hidden";
}
  if (ie4) {thislayer=eval('document.all.'+string+'.style')}
  if (ns4) {thislayer=eval('document.'+string)}
  if (ff) {thislayer=eval('document.getElementById("'+string+'").style')}
  thislayer.visibility="visible";
  last=string;
}