function na_change_img_src(name, nsdoc, rpath, preload)
{
  var img = eval((navigator.appName == 'Netscape') ? nsdoc+'.'+name : 'document.all.'+name);
  if (name == '')
    return;
  if (img) {
    img.altsrc = img.src;
    img.src    = rpath;
  }
}

function na_restore_img_src(name, nsdoc)
{
  var img = eval((navigator.appName == 'Netscape') ? nsdoc+'.'+name : 'document.all.'+name);
  if (name == '')
    return;
  if (img && img.altsrc) {
    img.src    = img.altsrc;
    img.altsrc = null;
  }
}

function na_show_layer(lname, flag)
{
  var layer = (navigator.appName == 'Netscape') ? document.layers[lname] : document.all[lname];
  if (lname == '')
    return;
  if (navigator.appName == 'Netscape')
    layer.visibility = (flag == 0) ? 'show' : 'hide';
  else
    layer.style.visibility = (flag == 0) ? 'visible' : 'hidden';
}