为什么添加的背景图片没效果？
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>无标题文本</title>
<style type="text/css">
.content{border:4px solid #badbdb;}
.book{background:url(images\t_book.gif) no-repeat #eff9f9;}
img{border:1px solid #b1adaa; margin:10px 18px;}
</style>
</head>
<body>
<div class="content book">
<img src="images\book1.jpg" width="80" height="80"/>
<img src="images\book2.jpg" width="80" height="80"/>
<img src="images\book3.jpg" width="80" height="80"/>
<img src="images\book4.jpg" width="80" height="80"/>
<img src="images\book5.jpg" width="80" height="80"/>
</div>
</body>
</html>
