There can surely be few brands out there who still don’t appreciate the importance of having a mobile-friendly website to direct people to when they carry out a search on a mobile device, given the proportion of search activity that now takes place on mobile devices.

Well any that have still not taken the requisite steps to ensure their site delivers a pleasing experience to those who arrive on it from a mobile search will no doubt start to suffer the consequences from tomorrow onwards when Google begins to expand the importance it attaches to mobile-friendliness as a ranking signal.

The changes were announced by Google two months ago in a blog post that said: “This change will affect mobile searches in all languages worldwide and will have a significant impact in our search results. Consequently, users will find it easier to get relevant, high quality search results that are optimized for their devices.”

Last week, mobile marketing firm Somo carried out it’s own study into the likely impact of the changes, flagging up David Beckham, the Scottish National Party, Next, Ryanair and The Daily Mail as some of the brands that would suffer if they did not take action to make their sites more mobile-friendly before the 21st.

Gareth Morgan, managing director of search agency Liberty Marketing told us the brands that will benefit from the changes will be those that offer a good mobile experience. “Brands that have invested in a responsive website and keeping load times down should see a rise in organic rankings and traffic from tomorrow,” he said. “Any brand without a mobile friendly site will be in the firing line, though it is important to remember that this is just a part of around 200 ranking factors, so sites won’t just disappear if their site isn’t mobile optimised, but they will fall below stronger rivals.”

Morgan’s advice to marketers is to take a look within their Analytics data to see how much organic mobile traffic they get from Google, as that’s what’s at stake. “They should also use this free tool from Google to see how mobile friendly their site is,” he added. “It’s also a good idea to put some rival websites in there, to see how you stack up in your marketplace. If everyone else has mobile optimised sites but you don’t, then chances are some of them will start outranking you.”

For more insight into what the changes mean for search listings, marketing and more, you can read our guest column on the ranking changes by Chris Lucas, vice president of marketing at Formstack, here.