function $(id){
		var obj = document.getElementById(id);
		return obj;
	}
	function cerrar_ventana(){
		$('ventana').style.display="none";
		$('mainContent').style.borderBottom="0";
		$('navegador_fotos').style.borderBottom="#000000 1px dashed";
	}
	function amplia_imagen(id){
		$('imagen_ventana').src = 'fotos/'+id+'.jpg';
		$('ventana').style.display="block";
		$('navegador_fotos').style.borderBottom="0";
		$('mainContent').style.borderBottom="#000000 1px dashed";
	}
	function ventana_datos(id){
		$('ventana'+id).style.display="block";
	}
	function cerrar_ventana_datos(id){
		$('ventana'+id).style.display="none";
	}
	function centrar(){
		var myWidth = 0, myHeight = 0;
		if( typeof( window.innerWidth ) == 'number' ) {
			//Non-IE
			myWidth = window.innerWidth;
			myHeight = window.innerHeight;
		} else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
			//IE 6+ in 'standards compliant mode'
			myWidth = document.documentElement.clientWidth;
			myHeight = document.documentElement.clientHeight;
		} else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
			//IE 4 compatible
			myWidth = document.body.clientWidth;
			myHeight = document.body.clientHeight;
		}
		var padding = Math.round((myHeight*1 -700)/2);
		if(padding>0){
			document.body.style.paddingTop=padding+"px";
		//	alert("Window width = "+myWidth+" Window height = "+myHeight+" Padding:"+padding);
		}
	}