Search giants Google have now implemented a change to their search listings that will improve the ranking of sites that work well on mobile devices (and, by logical extension, will be demoting sites that don't).
How do I check whether my site is mobile-friendly?
Google has created a page which you can use to see if your website passes the mobile-friendly test. Google have suggested that fulfilling this criteria will have "a significant impact on results" in a blog post made in February.
How do I make my site mobile-friendly?
There is generally two ways to go about creating mobile-friendly sites. The ideal way (and the way Google prefer) is to create what is known as a "responsive" site. A responsive site doesn't treat any device as special - it just optimises the view of the site based on the available width, regardless of what you're using to view it. A desktop machine using a browser set to a low width won't just default to the "full" site. It will adapt in exactly the same way as it would on a mobile device to provide the optimum experience.
Sometimes, this approach is not possible. In these cases, a mobile specific version of a site can be created. You will often see the address of the website flip to something like "m.thesite.co.uk" on a mobile device. This is an indication that you've been redirected to a version of the site that has been created specifically for mobile devices only. This approach should only be adopted when absolutely necessary. There's all sorts of problems inherent in adopting this technique - not least as no device detection is 100% accurate, so people may be directed to the "wrong" version of the site. It also means that there's two versions of a link for any given page. If someone using a mobile shares a link with someone using a desktop, the desktop user will be directed to the mobile site and receive a sub-optimal view.
As far as the process of actually enabling a responsive design (or otherwise) on your website is concerned, there's usually more to this than just "clicking a button". While it is fairly simple to get a basic page to flow nicely at all widths, most websites have areas that need more consideration. The front page of a website is often different to the others, and will usually need extra attention. If your website has a lot of data-heavy tables, one needs to find a way to render these in a sensible way at low widths.
If digging into your website code to try and make it responsive yourself seems too daunting, 3aIT can assist. Any new websites we create now are mobile-friendly by default. Additionally, we have recently been creating responsive versions of many of our older websites to ensure they do not fall foul of this change by Google. If you think we can help you, let us know.