看看http://codex.wordpress.org/Function_Reference/in_category

示例：

<?php if ( in_category(\'rabbis-weekly-commentary\') ) : ?>                   
<div id="inner_header">
<img src="http://www.ifcj.ca/ifcj_ca/images/elements/commentary_header.gif" border="0">
...
<?php elseif ( in_category(\'yaels-weekly-commentary\') ) : ?>                    
<div id="inner_header">
<img src="http://www.ifcj.ca/ifcj_ca/images/elements/commentary_header.gif" border="0">