Robert_Charlton - 3:50 am on May 3, 2013 (gmt 0)
Overlap with my writing and lucy24's posting...
wenwon, thanks for your follow-up question.
Under your theory, do you believe that our particular situation warrants the use of the Vary HTTP header?
Yes, it probably does... and my apologies for not noting the particular situation where it would be warranted. In Google's article, that would be the situation you describe, configuration #3, the Separate mobile URLs... assuming that you will choose some sort of User-Agent Detection to redirect your site.
As described in the very last section of the article...
Redirects and the HTTP Vary header
Please note that if your site automatically redirects mobile visitors coming to the desktop site to the mobile site, or vice versa, please be sure to configure your server to include the Vary HTTP header as described on this page [developers.google.com].
To make a separate note of the page, it is...
Redirects and User-Agent Detection
Last updated April 12, 2013
The Redirection article also emphasizes the need for Vary HTTP headers with automatic redirects, for reasons already discussed... caching and Googlebot.
Under Supported redirection techniques, the article discusses both...
- HTTP redirection
I have no time now to get into whether you should try for responsive design, or to implement another approach, but I do feel that you should implement some sort of automatic redirection related to viewport... ie, you should not rely on users deciding they don't like your static site and clicking over.
I myself would probably recommend different approaches for a new site than for an old site. The approach or combination of approaches you choose may depend on the degree of interactivity of your site. Definitely follow up the technologies that coopster suggests, which are probably more cutting edge than I think you're prepared to try... but there are some points made that you definitely should read.
One comment I should make now, though. You mention this URL setup for mobile...
IMO, this is going to be hopelessly confusing to implement, unless you are defaulting to your static site for the home page and then relying on manual choice, not IMO a good approach.
Though Google indicates no preferences, you're going to find it much easier to have a one-to-one correspondence between desktop and mobile pages by using a mobile subdomain. So you might have...
- for desktop, either
- and for mobile
If you can't do this easily at your present host, I recommend that you get a new DNS and hosting setup before you even consider trying to offer a mobile site. The additional control at the host level is something you will find necessary as you move ahead.
Regarding what "headers" are, here's an article that I've cited in this forum several times. It's one of the few articles I've seen that even tries to discuss the http protocol and how the web works in layman's terms....
How the web works: HTTP and CGI explained