function externalLinks()
{
        if (!document.getElementsByTagName) return;
        var anchors = document.getElementsByTagName("a");
        for (var i=0; i<anchors.length; i++) 
        {
                var anchor = anchors[i];
                if (anchor.getAttribute("href") &&
                 anchor.getAttribute("rel") == "external")
                anchor.target = "_blank";
        }
}
var state = 'none';
var obs = 'none';
function change(layer_ref)
{
        if (state == 'block') 
        {
                state = 'none';
                obs = 'none';
        }
        else 
        {
        state = 'block';
        obs = 'block';
        }
        if (document.all) { //IS IE 4 or 5 (or 6 beta)
                eval( "document.all." + layer_ref + ".style.display = state");
                eval( "document.all.oscurato.style.display = obs");
        }
        if (document.layers) { //IS NETSCAPE 4 or below
                document.layers[layer_ref].display = state;
                document.layeers['oscurato'].display = obs;
        }
        if (document.getElementById &&!document.all) 
        {
                hza = document.getElementById(layer_ref);
                hza.style.display = state;
                hza1 = document.getElementById('oscurato');
                hza1.style.display = obs;
        }
}