After Google’s infamous algorithm tweak in April, organic search traffic for some websites fell as much as 10 percent. Pictured: The Google logo is seen on a tablet screen in Paris, Dec. 4, 2012. Lionel Bonaventure/Agence France-Presse/Getty Images

The search is over for millions of websites. When Google rolled out an algorithm change to favor mobile-friendly websites three months ago, brands and businesses that weren’t up to speed braced for “Mobilegeddon.” And that’s exactly what they got.

The infamous update, which took effect April 21, caused a decline of up to 10 percent in organic search traffic for websites that weren’t properly optimized, the latest “Digital Advertising Report” from Adobe says. Although the drop wasn’t precipitous, it was noticeable over time, said Tamara Gaffney, a principal at Adobe Digital Index, who spoke with Adobe’s about the issue. The decline of organic traffic peaked on Memorial Day, and improved somewhat only to become more pronounced again in late June.

Digital advertising revenue was affected as well, with Google’s ad network delivering fewer ads and higher costs for websites whose mobile-friendliness hasn’t been addressed. Ad click-through rates, the report showed, fell 9 percent while the costs per click were up 16 percent, compared with the same three-month period last year.

Google Inc. - Trailing Month | FindTheCompany

Google pitched its algorithm change as a way to help mobile users find more high-quality content that is optimized for their devices. With mobile devices swallowing desktop usage, the Silicon Valley search giant had no choice but to act: As Pew Research noted last year, 64 percent of American adults own a smartphone, and a growing number are completely dependent on mobile devices for connectivity.

But as with any change in Google’s massive ecosphere, the mobile update was met with criticism by some businesses that felt they were being unfairly penalized for not playing by Google’s rules, with some companies saying they simply did not have the resources to optimize their websites.

“A lot of companies would like to see this as a Y2K moment,” Bill Nagel, co-founder of the online marketing company Netsertive, told International Business Times in April.

Adobe’s second-quarter digital index was released Wednesday. The quarterly research also included a “Social Intelligence Report,” which showed that even as Google is rushing to improve its mobile-friendliness, its display ad business is facing increased competition from the likes of Facebook. Click-through rates for Facebook were up 99 percent for the second quarter, compared with only 24 percent for Google.

Thanks to slowed growth in its key search business, Google missed earnings estimates for seven out of the last nine quarters.

Christopher Zara is a senior writer who covers media and culture. News tips? Email me. Follow me on Twitter @christopherzara.