Google to penalise mobile sites with pop-up ads

Starting next year, Google could start sending less traffic to mobile websites if they made use of interstitials - the pop-ups that could take up  users' screens, often with advertising.

The change would hurt online publishers and website operators who relied on interstitials to generate advertising revenue as users entered their websites via Google searches.

In a post published on Tuesday on the Google Webmasters blog, Google product manager Doantam Phan wrote, ''Pages that show intrusive interstitials provide a poorer experience to users than other pages where content is immediately accessible. This can be problematic on mobile devices where screens are often smaller.''

Consequently, pages where content was not easily accessible to a user on the transition from mobile search results might not rank as highly in Google's search results after 10 January 2017, which could end up driving less traffic to those pages and sites.

Examples of interstitials that made content less accessible included pop-ups that ''cover the main content [of a page], either immediately after the user navigates to a page from the search results, or while they are looking through the page,'' Phan wrote.

Google said in September 2015 that it would start penalising mobile webpages that showed app install interstitials, which might encourage a user to download a site's app rather than viewing content on the mobile web.

The move was aimed at combatting jarring experiences that sometimes forced themselves upon users when they were navigating to a page on their phone or tablet that Google marked as "mobile-friendly." Those surprises included showing a popup that covered the main content of the page, displaying an alert bubble or other elements that the user would dismiss, and placing content "below the fold," requiring users to scroll down to see it.

"To improve the mobile search experience, after January 10, 2017, pages where content is not easily accessible to a user on the transition from the mobile search results may not rank as highly," Phan wrote.