XML与CSS类选择符的使用

Class.xml
<?xml version="1.0" encoding="utf-8"?>
<?xml-stylesheet type="text/css" href="class.css"?>
<bookdetail>
<book class="A">
<author>曹雪芹</author>
<title>红楼梦</title>
<price>60.00</price>
</book>
<book class="A">
<author>罗贯中</author>
<title>三国演义</title>
<price>40.00</price>
</book>
<book class="M">
<author>琼瑶</author>
<title>一帘幽梦</title>
<price>20.00</price>
</book>
</bookdetail>
Class.css
@charset "utf-8";
/* CSS Document */
bookdetail
{
display:block
}
book.a
{
color:blue;
}
book
{
display:block
}
price
{
font-style:italic
}