Capa que dibuja los nodos. Las cuatro coordenadas son las esquinas
  http://maps.matarosensefils.net/cgi-bin/mapserv?map=/mnt/raid/www/public/http/guifimaps/GMap.map&REQUEST=GetMap&SERVICE=WMS&VERSION=1.1.1&LAYERS=Nodes,Links&FORMAT=image/png&BGCOLOR=0xFFFFFF&TRANSPARENT=TRUE&SRS=EPSG:4326&BBOX=2.45269775390625,41.53531012183376,2.4554443359375,41.537366035503794&WIDTH=256&HEIGHT=256

====== Con google maps ======
        GEvent.addListener(marker, "click", function () {
              marker.openInfoWindowHtml("Hello");
        });