It's obvious from a user experience perspective that mobile sites are important, but Google just released the proverbial hammer on non-mobile sites to prove it.
Google said that on April 21, 2015 (today) their mobile ranking factors will label your site as mobile-friendly or not, then use that information to determine how your site should rank (higher or lower).
Why is this?
There are now over 2 billion smartphone users, and over 83% of all internet usage comes from mobile.
Google knows this. Google also has a goal to get people to information as fast as possible, in the best medium possible, to answer their query at the fastest possible rate.
Without a mobile-friendly infrastructure on your site the chances are people won't find that information easily and quickly using mobile search.
This is why Google is going to start cracking down on non-mobile-friendly sites:
We will be expanding our use of mobile-friendliness as a ranking signal. 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.
What to do then?
Get on mobile, quick.
Primarily you should be focusing on what is referred to as "responsive design" which is, simply speaking, where your site scales depending on the resolution of the screen it is being viewed on.
With a "responsive" site you won't have to have multiple variations of a site, which makes it significantly more powerful for search engines than having a desktop and a mobile site, broken apart by an m-dot sub-domain.
An example of this would be if simpletiger.com was not responsive (which it is) and we instead had a mobile sub-domain where we redirected all mobile traffic to, that traffic would go to a sub-domain that looked like "m.simpletiger.com"
The problem with this is that when you split up your subdomains between www.simpletiger.com and m.simpletiger.com all link equity pointing to www.simpletiger.com gets split, and doesn't benefit m.simpletiger.com. Also without the proper setup Google can accidentally hit you for duplicate content if you have all of the same information represented on m.simpletiger.com and don't have it set up to tell Google's crawlers the reasoning for that.
This is why it's far simpler, more effective, more user friendly, and more search-engine friendly to use responsive design to push your mobile web strategy.
How do you do this?
It's a pretty straight-forward process.
Any designer / developer team that is worth their weight can get your responsive site together, but to get some of the best results out of your responsive design, I really recommend you read this incredibly thorough post from Digital Telepathy's blog about the most important points to keep in mind when designing your responsive site.
A few of their main points include:
Simplifying your navigation
Optimizing images to reduce load-time
Design with large buttons and non-text links (keep fingers in mind)
Use vector icons that can easily scale based on resolution
If you don't have your own team to put together your responsive site update, I would recommend reaching out to Crew – they have multiple freelance designer / developer teams, as well as agencies that could surely update your site without breaking your bank.
Wrapping up, and food for thought
When you think about how Google will role this out, the chances are initially it will only mainly affect sites that have a high relevance for mobile traffic.
The search terms that usually get the most mobile searches will probably be first on the list to be affected, if you think about this it's probably going to mainly be local results, whether that be for a restaurant, a gym, a hair salon, or other local queries.
Eventually this will affect everyone, and everyone will need a mobile-friendly responsive site, however first up will undoubtably be the big-hitting mobile market (that we aren't necessarily privy to).
That doesn't mean that this isn't any less paramount for everyone.
Respond quickly, and get your site responsive now.