The countdown is on to a change in the Google algorithm that will reward mobile-friendly sites with a higher search ranking – pushing those that aren't down the list of results.

An update to the algorithm, announced earlier this year, is pencilled in for April 21st and is "going to make waves", says Shane Curtin from digital marketing agency Vroom Digital. "Typically when Google makes an update, we receive a flurry of enquiries from companies after their ranking is lost."

For some of its clients, more than half of the traffic to their sites come from mobile devices. “You wouldn’t send your best salesperson out unshaven and with a shoddy suit. It’s the same for your online presence,” is what Curtin says to companies without mobile-friendly sites.

Agencies such as Vroom have been advising clients for at least two years to optimise their websites for mobile devices, but Google’s move should compel companies that have lagged behind to start the process, he adds.

Vroom is a Google partner for Adwords, the tech giant's platform for search advertising. In some sectors, it is common for people to spend money on online ads, he says, yet not do everything they can to get their sites on the first page for key search terms.