function ventanea(ancho,alto,nombreventana,pagina) {
	anchoPantalla=(screen.width/2)-(ancho/2)
	altoPantalla=(screen.height/2)-(alto/2)
	var win= eval('window.open(""+pagina+"",""+nombreventana+"","width="+ancho+",height="+alto+",resizable=0,toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=0,left="+anchoPantalla+",top="+altoPantalla+",noresize")')
}

function ventaneaScroll(ancho,alto,nombreventana,pagina) {
	anchoPantalla=(screen.width/2)-(ancho/2)
	altoPantalla=(screen.height/2)-(alto/2)
	var win= eval('window.open(""+pagina+"",""+nombreventana+"","width="+ancho+",height="+alto+",resizable=1,toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,left="+anchoPantalla+",top="+altoPantalla)')
}

function isNumber(str) {
	for (i = 0; i < str.length; i++) {
		if (str.charAt(i) < "0" || str.charAt(i) > "9") {
			return false;
		}
	}
	return true;
}