It's on the 18+ tab of the Site Settings page: "Your site will not be removed, but it will be listed on a special browse page." Nothing more specific than that mentioned anywhere.
ah thankyou, I knew I'd seen it somewhere.
A tag can only be a single word, and can only contain letters and numbers.
Select the tags you would like to remove:
You are going to block this site. This will do the following:
Are you sure you want to do this?