Thanks for replying, iridiax!
In this case, I was dealing with several dozen categories, so I needed a way to do it automatically. After much trial and error, this code did the trick:
<?php if (strlen(category_description()) > 0) {
echo “<div id=’catdesc’>”;
echo category_description();
echo “</div>”;
}
?>`
Turns out the styling has to be applied inside the IF statement.