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 content catalogs use slug as the URL field to optimize the URL of the catalog item for Internet search engines.
When using the new Search Engines Optimization features provided with SharePoint 2013 the browser title for the particular page will replace all contents of the PageTitlePlaceHolder Content Place Holder. This is important to know particularly when building hierarchical titles.
It is a good practice to have your website work with both www and non-www domain (ie. vs. ) domain. Only one of those domains however should be defined as canonical domain for your website.