function muestra(itm){document.getElementById('transition').style.display = 'block'}
function oculta(itm){document.getElementById('transition').style.display = 'none'}

var ie=document.all;
var nn6=document.getElementById&&!document.all;
var def;
var status;
var tempor = null;

if(ie) def=4;
else def=0;

function changeM(d,lab){
	var ug = document.getElementById('ulGalery').childNodes;
	var act;
	var actR;
	var liArr = new Array();
	for(r=0;r<ug.length;r++){
		if(ug[r].tagName=='LI'){
			liArr.push(ug[r]);
			
		}	
	}
	
	for(s=0;s<liArr.length;s++){if(liArr[s].className=='activel'){actR=s}}
	
	if(d==0 && actR>0) {
		//muestra('transition');
		act = liArr[(actR-1)];
		changeImage(act.id,act,lab);
	}
	if(d==1 && actR<liArr.length){
		//muestra('transition');
		act = liArr[(actR+1)];
		changeImage(act.id,act,lab);
	}
	
	
}
<!--PARA ABAJO COMIENZAN LAS GALERIAS-->

<!--Funcion Galeria-->

function cambiaGalery(image,lab){document.getElementById(lab).style.backgroundImage = 'url(media/images/'+image+')';}

function changeImage(image,itm,lab){
	
	var itmParent = itm.parentNode;
	if(document.getElementById('transition').style.display=='block'){
			clearTimeout(tempor);
			changeOpac(status, 'transition');
			//return false;
		}
		else{
	muestra('transition');
	changeOpac(100, 'transition');}
	setTimeout("cambiaGalery('"+image+"','"+lab+"')",100)
	opacity('transition', 100, 0, 2000);
	for(a=0;a<itmParent.childNodes.length;a++){
		if(itmParent.childNodes[a].tagName=='LI'){itmParent.childNodes[a].className='inactivel'}
	}
	
	itm.className='activel';
}

function opacity(id, opacStart, opacEnd, millisec) {
	var speed = Math.round(millisec / 100);
	var timer = 5+def;

	if(opacStart > opacEnd) {
		for(i = opacStart; i >= opacEnd; i--) {
			tempor = setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
			timer++;
			
		}
	} else if(opacStart < opacEnd) {
		
		for(i = opacStart; i <= opacEnd; i++)
			{
			tempor = setTimeout("changeOpac(" + i + ",'" + id + "')",(timer * speed));
			timer++;
		}
	}
}

function changeOpac(opacity, id) {
	var object = document.getElementById(id).style; 
	object.opacity = (opacity / 100);
	object.MozOpacity = (opacity / 100);
	object.KhtmlOpacity = (opacity / 100);
	object.filter = "alpha(opacity=" + opacity + ")";
	status = opacity;
	if(object.filter=="alpha(opacity=0)"){oculta('transition');}
	if(object.MozOpacity==0){oculta('transition');}
}