A list of online vertical ad networks. Vertical ad networks are focused on specific topic categories, or verticals, allowing advertisers and marketers to reach only a select niche audience likely to favor their products. This can be more useful for advertising niche products.They differ from horizontal ad networks, which serve advertisers and focus on distributing ads to th elargest possible audience. they are often ineffective unless they advertise products with a broad base of appeal. They are often ineffective unless they advertise products with a broad base of appeal.