Add Body Class in WordPress

Add a body class, in this case based on the first letter of the post title, so that the entry title can be styled with a letter-based background image.

add_filter('body_class','custom_body_classes');
function custom_body_classes($classes, $class) {
	if ( is_page() ) { // Only apply to Pages, not Posts
	    global $post;
	    $initial = strtolower(substr($post->post_title, 0, 1));
	    $classes[] = 'first-letter-'.$initial;
    }
    // return the $classes array
	return $classes;
}

Can obviously be adapted to apply to different entries (not just Pages).