Some advertisers decide to send custom ‘No Ad’ responses that require additional logic to handle. These custom ‘No Ad’ responses do not follow the IAB standards and can make it difficult for some ad servers to determine if the ad response was empty or not.
Some of the different methods used are: sending a custom non VAST error message in the body of the response or replying with a 400 http response code. Although, many ad servers can be tweaked to recognize these different ‘No Ad’ notification methods, it is not good practice. Particularly when there is an industry standard for how to do it and the advertisers always follow the standard when sending filled ad responses.
Some VAST parsers are very rigid in how they parse the VAST XML they recieve and even a small deviation from the VAST spec can prevent it from parsing and displaying properly. For this reason it is important that advertisers are careful to send VAST XML that meets the IAB VAST specification and this should also include their ‘No Ad’ response. If the mobile ad industry is going to continue to grow and expand, it is imperative that the different ad protocols are used and followed.