为什么text-align没有效果_html/css_WEB-ITnose

<?xml version="1.0" encoding="UTF-8"?><?xml-stylesheet type="text/css" href="style.css"?><books>    <book>        <bookname>Java Web</bookname>        <author>Wang</author>        <publishing>QingHua</publishing>        <company>MingRi</company>        <ISBN>7-302-21033-7</ISBN>        <price unit="RMB">69.80</price>        <url>![CDATA[http://www.mingribook].com/bookinfo.php?id=227&sid=4]</url>    </book>    <book>        <bookname>DBMS</bookname>        <author>Wang</author>        <publishing>RenMing</publishing>        <company>MingRi</company>        <ISBN>7-115-14689-6</ISBN>        <price unit="RMB">49.80</price>        <url>![CDATA[http://www.mingribook].com/bookinfo.php?id=208&sid=11]</url>    </book></books>

author,pulishing,company,ISBN,price{    text-align: center;    width: 18%;}