This shows how to use an externally provided list to create custom URL categories. This external list may be provided by vendors to "white-list" websites, or to "black-list" other websites.
I like the presentation, but my experience with this is that your list is a domain list and not a url list. It stopped gizmodo.com because that is where you were going, but www.reddit.com is a different url than reddit.com. With the url list you can get more granular on what is blocked, but you also have to add in ssl intercept for the uri part of the url.