//Funcion para mostrar y esconder una capa
var state = 'none';
function showhide(layer_ref) {
if (state == 'block') {
state = 'none';
}
else {
state = 'block';
}
if (document.all) { //IS IE 4 or 5 (or 6 beta) 
eval( "document.all." + layer_ref + ".style.display = state");
}
if (document.layers) { //IS NETSCAPE 4 or below 
document.layers[layer_ref].display = state;
}
if (document.getElementById &&!document.all) {
hza = document.getElementById(layer_ref);
hza.style.display = state;
}
}


function select(a) {
    var theForm = document.myForm;
    for (i=0; i<theForm.elements.length; i++) {
        if (theForm.elements[i].name=='box[]')
            theForm.elements[i].checked = a;
    }
}