As a last minute Christmas present for you, I've enhanced WSN's advertising system in several ways.

First, I've added device and country targeting. Device targeting allows you to set certain ads to only show on mobile or only show on desktop/laptop. This is useful when you have differently sized or differently targeted ad code for phones versus desktop. Country targeting, which depends on IP geolocation being turned on, is useful if you have certain ads or ad networks that are only good for a particular country or set of countries. For example, if you're advertising an offer only available in the USA you can limit the ad to only show in the USA so that your international visitors are served something else potentially more useful.

After those changes, the frequency percentage system had come to look absurdly complicated. A set of percentages that adds up to 100 in one country might not add up that way in another, thanks to country targeting. Likewise with device targeting your ads in a slot might add up to 100% on desktop but 120% on mobile. It was clear that percentages were not the ideal way forward.

Also, I found that WSN's ad display logic was regluarly repeating display of the same ad until it could bring that ad's impressions count up to the desired percentage. That's bad, because an ad may have been created much more recently than a different ad or percentages may have been changed. Essentially, this was causing new ads to be the only ones shown for long periods.

The solution to both issues? A new frequency system that calculates relative odds for display of each ad. First, WSN determines which ads are eligable to be viewed by the person viewing this ad slot on the current page (removing any ads from other ad slots or targeted at other devices or countries from consideration). For each remaining ad, it calculates a weight: a random number between 0 and the frequency number you've specified. Whichever ad ends up with the highest weight gets displayed. This means you get a good variety of ads at all times.

I think this makes for a much better banner rotator now.