Earlier this month, Google began sending warnings to some webmasters that their sites were not mobile friendly. Not all webmasters received one of these notices, so there’s little bit uncertainty about what criteria was needed in order to prompt one of these warnings.

However, now we know that Google is taking action against those sites if they are not mobile friendly in the form of a new mobile only algorithm. People began noticing that websites that received this notice are no longer ranking when a search is done on a mobile device. The rankings are retained for desktop searches, but the visibility is mobile searches drops dramatically. So it does seem that it is only specifically affecting mobile searches, at least at this time.

Ryan Jones, Manager, Search & Analytics at  SapientNitro began noticing the drop recently. “Over the past few days I’ve seen some sites that have gotten warnings retain their #1 desktop rankings for competitive keywords but fall several pages down for the same keywords in mobile.”

It raises the question about whether this is the same fluctuation that prompted the chatter on Friday about a possible update although Google stated they didn’t believe it was either Panda or Penguin related in a Google Hangout.

But with such an emphasis being placed on mobile-friendly sites by Google, particularly in the last year, many SEOs have been expecting last year that an additional mobile-only algorithm to begin affecting non-mobile friendly sites at some point.  They added mobile tools to Google Webmaster Tools to assist webmasters in making their sites mobile-friendly.

Alan Bleiweiss of AlanBleiweiss.com believes that the mobile warnings may be tied to page speed, which would explain why some mobile un-friendly sites received the warning in Google Webmaster Tools yet others did not.

As far back as the MayDay update, the writing was on the wall that page speed was a factor for SEO and would become more emphasized over time. That proved to be quite true for all search queries, regardless of platform or device. The same can be said about overall page processing, and a host of quality considerations. It was inevitable then, that this would be adapted specific to mobile search and we are now seeing that play out. Sites that are ranking for phrases for desktop searches are now not showing up for mobile searches even when they previously had.

We’re not talking about just mobile related to localization. We’re talking about quality factors.  Trust factors unique to a mobile experience.

Google is displaying “mobile friendly” labels on many sites as another example that they are taking it to a new level.  Unfortunately that specific action is critically flawed – they’re displaying many sites that are not mobile friendly from a site speed or page processing performance perspective specific to mobile but where those sites are doing better for those signals on desktop devices.  Which is directly opposite of how they’re NOT displaying other sites specific to mobile devices due to performance issues.

So it’s still an in-flux issue, however the only safe and proper course of action is for site owners to get their act together regardless of device type, but more now than ever, for mobile if that is where they have the most weakness, yet across the board if the problems are wide spread enough.

For users that may not have made their sites mobile friendly yet, if they are affected by this new mobile algo, it will likely show pretty clearly a dramatic drop in mobile traffic without a corresponding drop in desktop traffic. Site seem to beranking as usual in desktop, however the unfortunate thing is that some webmasters might not realize that a drop in traffic is strictly mobile related.

Update: Google is continuing to send more warnings for non-mobile-friendly websites.