Add the following to your theme's functions.php file to disable YARPP's default CSS Style Sheet from loading.
Disable YARPP's CSS Style Sheet (related.css):
add_filter( 'yarpp_enqueue_related_style', '__return_false' );Disable YARPP's Thumbnails Template Style Sheet (styles_thumbnails.css):
add_filter( 'yarpp_enqueue_thumbnails_style', '__return_false' );