While browsing the site, some users may see comic thumbnails like this:
Comics on The Duck use an age/content rating system. Comics rated E (Everyone), T+ (Teen) and M (Mature) are accessible to everyone. Comics rated A (Adult) are accessible only to account holders who are 18 years of age or older.
Someone who is not logged in, or who is logged in but is under 18, will only see the "A" thumbnail. If they try and access the comic to read it, they'll receive an message about the comic being age-restricted.