For some time, I have notice that my Google adsense advertising do not appear on certains pages of my blog. I am not worried and  I have  attributed this oddity  to Google. I have decided today to explore the reals reasons and I found the culprit. This is Cloudflare and more specially the option « Rocket Loader ™ (Web Optimization) ».

To remember, « Rocket Loader ™ (Web Optimization) » automatically asynchronously loads your JavaScript resources, resulting in faster page rendering. « Rocket Loader ™ (Web Optimization) » handles both in line and external scripts, while maintaining order of execution. In manual mode, you designate which scripts for « Rocket Loader ™ (Web Optimization) » to load asynchronously.

CloudFlare is able to detect incompatible browsers and disable Rocket’s loader. This option require JavaScript. Websites that have a lot of ads and other JavaScript widgets will benefit the most from « Rocket Loader ™ (Web Optimization) ».

So if on your site, the code javascript of adsense » won’t display or does not execute correctly and if the option « Rocket Loader ™ (Web Optimization) » is on mode « automatic« . The solution for this problem is to put the option « Rocket Loader ™ (Web Optimization) / Beta  » on OFF or MANUAL.

As a reminder, the feature is in beta. It is therefore not surprising that there is some recurring bugs.

Edit : Confirmation by Cloudflare :

« The basic CloudFlare setup will not impact Google AdSense at all. CloudFlare does have a beta feature called Rocket Loader™ that may break Javascript on some sites, so you should turn Rocket Loader off if you see an issue with the JavaScript or a dramatic change in AdSense numbers. You can turn Rocket Loader off by going to:
Settings->CloudFlare Settings->Performance Settings->Rocket Loader->Toggle Off.

Note: We would also strongly recommend installing mod_cloudflare so original visitor IP is passed back to your server logs. »