function muestra(capa) {
   var bd = new BrowserDetector(navigator.userAgent);
   switch(bd.majorver) {
      case '4':
      switch(bd.browser) {
  	   case 'Netscape':
	      document.layers[capa].visibility = "visible";
		break;
  	   case 'IE':
		document.all[capa].style.visibility = "visible";
		break;
	   case 'Opera':
		document.getElementById(capa).style.visibility = "visible";
		break;
	}
      break;
      case '5':
 	   document.getElementById(capa).style.visibility = "visible";
 	   break;
      case '6':
	   document.getElementById(capa).style.visibility = "visible";
	   break;
      } //final de switch
 }