function mostrarcapa(idCapa){ 
if (document.layers) capa = eval("document." + idCapa); 
    if (document.all) capa = eval(idCapa + ".style"); 
        if (document.getElementById) capa = eval('document.getElementById("' + idCapa + '").style');
        if ((capa.visibility == "hidden") || (capa.visibility == "hide")){ 
            capa.left = ((window.screen.width /2) + 300) + "px";
						capa.top = '15px';
            capa.visibility = (document.layers) ? "show" : "visible" ; 
        }else{ 
        		capa.left = ((window.screen.width /2) + 300) + "px";
						capa.top = '15px';
            capa.visibility = (document.layers) ? "show" : "visible" ; 
        }
}