Google says serving app install ads that obstruct the majority of the content of a page is not "mobile-friendly." Flickr CC/Ron Bennetts Google has been making a serious effort to ensure websites are as mobile-friendly as they can possibly be.

In April, Google unleashed what was dubbed "Mobilegeddon" on website owners. Essentially, its algorithm started favoring mobile-friendly websites (ones with large text, easy-to-click-links, and pages that re-size to fit whatever screen they're viewed on) and ranked them higher in its search results.

On Tuesday Google announced another update that website owners need to watch out for. It wants sites to stop serving those annoying, sometimes full-page app install ads when users click from a mobile search result to a website.

The blog post reads: "Sometimes a user may tap on a search result on a mobile device and see an app install interstitial that hides a significant amount of content and prompts the user to install an app. Our analysis shows that it is not a good search experience and can be frustrating for users because they are expecting to see the content of the web page."

Google has updated its "Mobile-Friendly Test" to indicate sites should avoid showing these kinds of interstitial ads.

From November 1, mobile web pages that show app install interstitials that hide a significant amount of content will no longer be deemed mobile-friendly.

Google suggests that site owners can use these big full-screen interstitials later on in the browsing experience and they won't be punished — just not directly after the search result. The company also says smaller app install banners "provide a consistent user interface for promoting an app and provide the user with the ability to control their browsing experience."

Google gives the example below of the experience it wants webmasters to avoid:

And here's an app install banner, which it says will be less intrusive.

Mobile app install ads are a huge sector of the digital advertising market. Mobile app install advertising revenue is set to top $4.6 billion this year, and grow to $6.8 billion by the end of 2019, according to data from BI Intelligence. However, the majority of the ads Google is referring to in its latest update won't include any spend, and are instead a technique for publishers to promote their apps on their own sites.