div 为什么不显示背景图片 帮我看看样式和代码有没有错误？

<div class="zong"><?php templ_header_start(); // Header Start hooks?>
<div class="header clear">
<div class="header_in">
<div class="logo">
<?php templ_site_logo(); ?>
</div>
<div class="header_right">
<?php if (function_exists('dynamic_sidebar')){ dynamic_sidebar('header_logo_right_side'); }?>

<?php /*?><div class="for_reservation">
<h3> For Reservations</h3>
<p class="i_booking"><a href="#">Book Online</a></p>
<p class="i_phone">0844 575 8888 </p>
</div><?php */?>

</div>
</div> <!-- header inner #end -->
</div> <!-- header #end -->

<div class="main_nav">
<?php templ_get_main_header_navigation(); ?>
</div>
</div>
----------------------------------------------------------------------------
.zong { background-image: url(images/head_bg.jpg);
background-repeat: repeat-x;}
.logo { padding: 25px 0; overflow: hidden; float: left;}
.site-title h1 { margin:0; padding:0 ; font-weight:normal; }
.site-title a { font-size:40px; text-decoration:none; }
.site-title a:hover { text-decoration:none; }
.site-description { font-size:14px; }
.site-description { padding:0 0 25px 0; overflow: hidden;}
.site-description .textwidget {font-size: 11px; line-height: 1.3;}
要背景图片显示在最外面的DIV框里面

相关了解……