Google Webmaster Tools is sending out notices to let you know your website is not mobile-friendly.
They ask you in the notice to follow the steps to make sure your website is mobile-friendly.
If you do not make your website mobile-friendly Google will not have your website indexed for mobile search.
What that means is that you will still be on the search engine for your keywords when people search from their desktop computers but you will not be visible to those same people if they search on their smart phones or iPads.
Making your site mobile-friendly in most cases is very simple and you can do it yourself.
Don't get sucked into those companies that call you to charge you big bucks to make your website mobile-friendly.
If your site is hosted on WordPress, it is as simple as updating your theme. If you are using any of the WordPress themes that come with WordPress installations they are mobile friendly.
If you have purchased a theme from another company – they should have an update for you which makes the theme mobile-friendly.
Here is the link to the Google Developers guide on making your site mobile-friendly:
They have solutions for most kinds of websites: wordpress, joomla, etc.
After you complete the steps you can check your website at this URL to see if it passes the Google test for mobile-friendly:
The page looks like this:
With so much search these days coming from mobile devices don't get left out!
Make sure that your website is mobile-friendly!