Here is the easiest way I have found to add a unique body class to individual pages in a Concrete5 site.
First, in your dashboard go to “Pages and Themes,”then “Attributes,” and add a custom attribute (text field) called bodyclass.
Next, open your theme’s header.php file and add:
class="<?php echo $c->getCollectionAttributeValue('bodyclass')?>"
to your < body > tag, so it reads like this:
<body class="<?php echo $c->getCollectionAttributeValue('bodyclass')?>">
For any page that you want to apply a custom class to, simply add the Body Class custom attribute and type whatever class name you want into the Body Class Custom Attribute text field. When you save your changes, your opening < body > tag will now look like: