window.addEvent('load', function(){
								 
		var encabezado = $('encabezado');		
		var photoFrames = $ES('div.contenido-bgnd', encabezado);
		
		var actual = $random(0,(photoFrames.length)-1);
		var next = $random(0,(photoFrames.length)-1);

		if(next == actual){ next++; }		
		
		photoFrames.each( function(photoFrame){
								   
				 if(photoFrame == photoFrames[actual]){
					photoFrame.setStyle('display','block');
					}
				 else {
					photoFrame.setStyle('opacity','0');
					}
					
						});

		var photoFrameFx = new Fx.Elements(photoFrames, {duration: 500,
								 wait: false, transition: Fx.Transitions.linear,
								 onStart: function(){
									photoFrames[next].setStyle('display','block');
									},																																																	
								 onComplete: function(){
    									photoFrames[actual].setStyle('display','none');
									actual = next;
									next = $random(0,(photoFrames.length)-1);
									if(next == actual) { next++; }
									else if(next == (photoFrames.length)-1){
										next = $random(0,(photoFrames.length)-1);
										}
									} 
									});
		
		var changeBgnd = function() {
			
				var o = {};
				
				o[actual] = { 'opacity': [1,0]}
				o[next] = {'opacity' : [0,1] }
				
				photoFrameFx.start(o);				
				
				};

			changeBgnd.periodical(20000);
									   
}); /*No borrar*/