Google has just announced that they have made a major change to their search algorithm. This is the most significant change since Panda, according to Marketing Magazine.
Basically, it penalizes sites (such as Marks & Spencer) which it does not see as mobile optimized. M&S has a separate mobile site and not one site with responsive design. Google has also launched a free app, which allows you to instantly check whether your site is sufficiently mobile friendly for Google. I ran on it on my web site and got the thumbs up!
Google also says that half of search traffic now comes from mobile and that is why they have changed the algorithm to take this into account. Why not test out you page? It is free and quick to do using the Google Mobile Search tool.