Internet search giant Google on Tuesday modified its AdSense policy regarding 300×250 above-the-fold ads, which it said will be a boon to publishers and advertisers in managing their mobile websites.

In a blog post by John Brown, head of Publisher Policy Communications at Google AdSense, he explained that the change is part of their goal to look for ways to help everyone improve their mobile experience.

After careful review, they’ve determined that 300×250 above-the-fold ads implemented in a user-friendly manner “do not annoy, distract, or result in ad performance issues.”

He was quick to add, however, that with the removal of the restriction, site owners “must be vigilant to ensure that their mobile site layouts do not cause ads to push the page content below the fold in such a way that may lead to accidental clicks.”

This change wouldn’t have been possible back when Google AdSense was started in 2003. But the current demand by consumers for bigger mobile phone screens may have prompted Google to change its policy regarding the size of ads on mobile sites. With a bigger display, the ads can be shown without necessarily filling up all the space.

But critics pointed out that the new policy doesn’t make sense because size restriction was primarily imposed due to huge ads pushing the content down, leading to users accidentally clicking on them. These run in contrast to Google’s advocacy of providing a user-friendly mobile experience.

Google seems to have changed this policy after recognizing that a 300×250 ad yields higher revenue per 1,000 impressions (RPM) and viewability rate (refers to the percentage of the ad that is actually viewed by the user). Page revenue per 1,000 impressions represents the accumulated earnings the website gets for every 1,000 impressions.

Placing the 300×250 ad above the fold is strategic since, based on Google AdSense study, these types of ads scored the lowest viewability rate if placed elsewhere on the website. Changing the placement bumps the viewability rate to as high as 70%. With higher RPM, Google stands to earn more.

More than the ad placement, however, Brown said that focusing on a mobile-friendly site through efficient design and substantive content will eventually boost user engagement. “In turn, this could lead to an increase in your mobile ad revenue in the long-term,” he added.