Robert_Charlton - 11:51 pm on Dec 29, 2012 (gmt 0)

Although they prefer a responsive design, they do support and recommend "Separate URLs for mobile".

klark0 - Thanks for the link to the Google smartphone recommendations. I'm about to re-say what I know you were intending to say, but I think there's enough chance for misunderstanding the above that I'm going to say it differently... at least to provide different emphasis.

Google says...

We recommend using responsive web design because it has many good aspects: - Using a single URL for a piece of content makes it easier for your users to interact with, share, and link to your content, and a single URL for the content helps Google's algorithms assign the indexing properties for the content....

About "Separate mobile URLs", if you use separate mobile urls, Google says...

In this configuration, each desktop URL has an equivalent different URL serving mobile-optimized content. A common setup would be pages on www.example.com serving desktop users having corresponding m.example.com pages serving mobile users. Google does not favor any particular URL format as long as they are all accessible to both Googlebot and Googlebot-Mobile....

...and Google then goes on to recommend under these circumstances also using the rel="alternate" tag on the desktop page and the rel="canonical" tag on the mobile page, with additional specific syntax for them.