They want to keep their customers happy
Google is a service like any other and as a result they want to keep their customers happy with the websites they recommend.
One way in which they do this is by prioritising those that have fully responsive, mobile optimised layouts that can be viewed by all browsers.
Mobile optimisation is important for the viewer as it allows them to quickly find what they’re looking for without any hassle. Convenience is key for the customer, as they don’t want to spend time zooming in and out or searching for tabs.
In a new announcement Google have given hints on their algorithm and what site owners can do to improve their rankings.
Mobile optimisation is a hot topic but it’s not enough to be mobile, it has to be a good site too.
If your site uses videos then this search engine will rank it differently depending on the type of technology they use. They favour HTML5 over Flash for this reason and this could be having a negative effect on your ranking.
Many sites use redirects to take the user to the mobile site homepage from the search results but this can lead to penalisation too. The user may be looking for a link deeper within the site only to be redirected to the homepage, which effects their browsing experience.
We’ve all been annoyed at mobile sites that come brandishing their app with a full page pop up and Google have taken this into account too. To combat these irritating features they now decrease the rank of sites that use these interstitials.