var filtro=false;
	function filter(){
		if(!filtro){
			document.getElementById("filtro2").style.visibility='visible';
			filtro=true;
		} else {
			document.getElementById("filtro2").style.visibility='hidden';
			filtro=false;
		}
	}
	
	function filter_off(){
		document.getElementById("filtro2").style.visibility='hidden';
	}
        mi_imagen1=new Image
        mi_imagen1.src="http://www.videomundial.net/templates/images/luzao.png"
        mi_imagen2=new Image
        mi_imagen2.src="http://www.videomundial.net/templates/images/luza.png"
        var i=1;
        function cambia_imagen() { 
        if (i == 1)
        {
        document.images['prueba'].src=mi_imagen2.src
        i=2;
        }
        else 
        {
        document.images['prueba'].src=mi_imagen1.src;
        i=1;
        }
        }