function Nav() {
	var agent  = navigator.userAgent.toLowerCase();
	this.major = parseInt(navigator.appVersion);
	this.minor = parseFloat(navigator.appVersion);
	this.ns    = ((agent.indexOf('mozilla')!=-1) && ((agent.indexOf('spoofer')==-1) && (agent.indexOf('compatible') == -1)));
	this.ns2   = (this.ns && (this.major == 2));
	this.ns3   = (this.ns && (this.major == 3));
	this.ns4b  = (this.ns && (this.minor < 4.04));
	this.ns4   = (this.ns && (this.major >= 4));
	this.ie    = (agent.indexOf("msie") != -1);
	this.ie3   = (this.ie && (this.major == 2));
	this.ie4   = (this.ie && (this.major >= 4));
	this.win   = (agent.indexOf("win")!=-1);
	this.mac   = (agent.indexOf("mac")!=-1);
	this.unix  = (agent.indexOf("x11")!=-1);
}

var is = new Nav();

if(is.ns4) {
	doc = "document";
	sty = "";
	html = ".document"
} else if(is.ie4) {
	doc = "document.all";
	sty = ".style";
	html = ""
}

//Prender imagen
function img_on(imageName,layerName)
{
	imageOn = eval(imageName + "_on.src");
	if(is.ns4) {
		document[layerName].document[imageName].src = imageOn
	} else if(is.ie4) {
		document[imageName].src = imageOn
	}
}

//Apagar imagen
function img_off(imageName,layerName)
{
	imageOff = eval(imageName + "_off.src");
	if(is.ns4) {
		document[layerName].document[imageName].src = imageOff
	} else if(is.ie4) {
		document[imageName].src = imageOff
	}
}


<!-- ******************************************* INICIO SCRIPT MENU 2 ************************************ -->

/********Rutinas generales para los casos Javascript***********/

function MM_swapImgRestore() { //v3.0
  var i,x,a=document.MM_sr; for(i=0;a&&i<a.length&&(x=a[i])&&x.oSrc;i++) x.src=x.oSrc;
}

function MM_preloadImages() { //v3.0
  var d=document; if(d.images){ if(!d.MM_p) d.MM_p=new Array();
    var i,j=d.MM_p.length,a=MM_preloadImages.arguments; for(i=0; i<a.length; i++)
    if (a[i].indexOf("#")!=0){ d.MM_p[j]=new Image; d.MM_p[j++].src=a[i];}}
}

function MM_findObj(n, d) { //v4.01
  var p,i,x;  if(!d) d=document; if((p=n.indexOf("?"))>0&&parent.frames.length) {
    d=parent.frames[n.substring(p+1)].document; n=n.substring(0,p);}
  if(!(x=d[n])&&d.all) x=d.all[n]; for (i=0;!x&&i<d.forms.length;i++) x=d.forms[i][n];
  for(i=0;!x&&d.layers&&i<d.layers.length;i++) x=MM_findObj(n,d.layers[i].document);
  if(!x && d.getElementById) x=d.getElementById(n); return x;
}

function MM_swapImage() { //v3.0
  var i,j=0,x,a=MM_swapImage.arguments; document.MM_sr=new Array; for(i=0;i<(a.length-2);i+=3)
   if ((x=MM_findObj(a[i]))!=null){document.MM_sr[j++]=x; if(!x.oSrc) x.oSrc=x.src; x.src=a[i+2];}
}

function MM_reloadPage(init) {  //reloads the window if Nav4 resized
  if (init==true) with (navigator) {if ((appName=="Netscape")&&(parseInt(appVersion)==4)) {
    document.MM_pgW=innerWidth; document.MM_pgH=innerHeight; onresize=MM_reloadPage; }}
  else if (innerWidth!=document.MM_pgW || innerHeight!=document.MM_pgH) location.reload();
}
MM_reloadPage(true);

function MM_openBrWindow(theURL,winName,features) { //v2.0
  ventana = window.open(theURL,winName,features);
  if (ventana.opener == null) ventana.opener = self;
	ventana.focus();
}

function MM_showHideLayers() { //v6.0
  var i,p,v,obj,args=MM_showHideLayers.arguments;
  for (i=0; i<(args.length-2); i+=3) if ((obj=MM_findObj(args[i]))!=null) { v=args[i+2];
    if (obj.style) { 
        obj=obj.style;v=(v=='show')?'visible':(v=='hide')?'hidden':v;
    }
    obj.visibility=v; 
  }
}


function expandir(id,tam) {
	var obj = objHtml(id)
	
	for (I=1; I<=tam ; I++)
	{
		cerrar("capa_"+I);
	}



	if (miNavegador.standard) {
		if (obj.style.display == "none")
		   obj.style.display = 'block'
		else
		   obj.style.display = 'none'
	}else{
		if (obj.display == "none")
		   obj.display = 'block'
		else
		   obj.display = 'none'
	} 
}

//////////////////////////SISTEMA OPERATIVO///////////////////////////////

function checkOS()
{
		if(navigator.userAgent.indexOf('IRIX') != -1)
		{
			var OpSys = "Irix";
		}
		else if((navigator.userAgent.indexOf('Win') != -1) && (navigator.userAgent.indexOf('95') != -1))
		{
			var OpSys = "Windows95";
		}
		else if(navigator.userAgent.indexOf('Win') != -1)
		{
			var OpSys = "Windows3.1 or NT";
		}
		else if(navigator.userAgent.indexOf('Mac') != -1)
		{
			var OpSys = "Macintosh";
		}
		else
		{
			var OpSys = "other";
		}
	//alert(OpSys);
	return OpSys;
} 

function setBrowserType()
{
	var aBrowFull = new Array("opera", "msie", "netscape", "gecko", "mozilla");
    var aBrowVers = new Array("opera", "msie", "netscape", "rv", "mozilla");
    var aBrowAbrv = new Array("op", "ie", "ns", "mo", "ns");
    var sInfo = navigator.userAgent.toLowerCase();
    sBrowser = "";
		
		for (var i = 0; i < aBrowFull.length; i++)
		{
     		if ((sBrowser == "") && (sInfo.indexOf(aBrowFull[i]) != -1))
			{
      			sBrowser = aBrowAbrv[i];
      			sVersion = String(parseFloat(sInfo.substr(sInfo.indexOf(aBrowVers[i]) + aBrowVers[i].length + 1)));
				
     		}
    	}
	
	return sBrowser;
}

var navega = setBrowserType();
var sis_ope = checkOS();

//alert (sis_ope);

function expandir2(id) {

	//if (navega=='ie') {
		if (document.getElementById(id).style.display == "none")
		   document.getElementById(id).style.display = 'block'
		else
		   document.getElementById(id).style.display = 'none'
	//}else{
//		if (document.getElementById(id).style.display == "none")
//		   document.getElementById(id).style.display = 'block'
//		else
//		   document.getElementById(id).style.display = 'none'
//	} 
}

function cerrar(id) {
	var obj = objHtml(id)
	if (miNavegador.standard) {
		obj.style.display = 'none'
	}else{
		obj.display = 'none'
	}	  
}

/***Objetos globales definidos aquí**********/
function oNavegador(  ) {
	this.nombre = navigator.appName;
	this.iniciar = iniciar;
	this.IE = this.nombre.toUpperCase().indexOf('MICROSOFT') >=0;
	this.NS = this.nombre.toUpperCase().indexOf('NETSCAPE') >=0;
	this.OP = this.nombre.toUpperCase().indexOf('OPERA') >= 0;
	this.XX = !this.IE && !this.NS && !this.OP;
	this.version = this.iniciar();
	this.Verent = parseInt(this.version);
	this.standard = (this.IE && this.Verent >=5) || (this.NS && this.Verent >=4)

/* ======================================================================
	FUNCION:	iniciar( ), miembro de oNavegador
	ARGS: 		none.
	DEVUELVE:	nada
	DESCRIP:	Inicializa los valores del objeto
====================================================================== */
  function iniciar() {
  var ver = navigator.appVersion;
	//alert (ver) ;
  if(ver+"" != "NaN")
	if (this.IE)
		{
		ver.match(/(MSIE)(\s*)([0-9].[0-9]+)/ig);
  		ver = RegExp.$3;
		}
  return ver;
  } //Termina la funcion iniciar el objeto
}

window.miNavegador = new oNavegador()
window.miNavegador.iniciar();
/*=========================================================================
FUNCION:	objHtml(n, d), 
ARGS:		n: un atributo ID del elemento que se desea encontrar
			d: documento en el que se busca
RETURN:		Referencia javascript al elemento HTML cuyo ID es el atributo n
DESCRIP:	Esta función busca un elemento HTML (un nodo) cuyo atributo ID sea igual al 
			que se pasa como primer argumento ( n ). La b´suqueda se realiza en el árbol
			que se le indique como segundo argumento, si éste no existe la busqueda se 
			realiza en document de la ventana actual. La función es recursiva.
================================================================================*/			
function objHtml(n, d) { 
  var p,i,x;
  if(!d) d=document;
  if (miNavegador.standard)
	  x = d.getElementById(n)
  if(!(x=d[n]) && miNavegador.IE)
      x=d.all[n];
  for (i=0; !x && i<d.forms.length; i++)
      x=d.forms[i][n];
  for(i=0; !x && d.layers && i<d.layers.length; i++)
      x=objHtml(n,d.layers[i].document);
  return x;
}

<!-- ******************************************* FIN SCRIPT MENU 2 ************************************ -->