On a multi-entry page inside the exp:weblog:entries tag, if you want to show information conditionally based on category, you’ll need to use PHP:
{exp:weblog:entries weblog="yourweblog"}
...
{categories}
<?php if ({category_id} == 54) {
?>
conditional content here
<?php
}
?>
{/categories}
{/exp:weblog:entries}
Category:Entries Category:Templates Category:Categories