When working with content catalogs, if your visitors use an invalid URL, instead of seeing the Page Not Found page they will see an empty page.
When working with content catalogs which are published on the Internet use standard SharePoint SEO fields to add search metadata to your catalog items and optimize them for Internet search engines.
When working with recommendations SharePoint 2013 Search records analytics events. By default those events don’t influence recommendations’ ranking.
When working with recommendations SharePoint 2013 Search records analytics events. Unfortunately those events are not being recorded for anonymous users.
On public-facing websites enable the Usage Cookie to track anonymous visitors.