Let’s start with a simple question: what do we mean by “mobile phone” when talking about mobile-friendly websites?
A good way to answer this question is to think about the capabilities of the mobile phone’s web browser, especially in relation to the capabilities of modern desktop browsers. To simplify matters, we can break mobile phones into a few classifications:
1. Traditional mobile phones: Phones with browsers that cannot render normal desktop webpages. This includes browsers for cHTML (iMode), WML, WAP, and the like.
2. Smartphones: Phones with browsers that render normal desktop pages, at least to some extent. This category includes a diversity of devices, such Windows Phone 7, Blackberry devices, iPhones, and Android phones, and also tablets and eBook readers.
We can further break down this category by support for HTML5:
* Devices with browsers that do not support HTML5
* Devices with browsers that support HTML5
Once upon a time, mobile phones connected to the Internet using browsers with limited rendering capabilities; but this is clearly a changing situation with the fast rise of smartphones which have browsers that rival the full desktop experience. As such, it’s important to note that the distinction we are making here is based on the current situation as we see it and might change in the future.
Googlebot and Mobile Content
Google has two crawlers relevant to this topic: Googlebot and Googlebot-Mobile. Googlebot crawls desktop-browser type of webpages and content embedded in them and Googlebot-Mobile crawls mobile content. The questions we’re seeing more of can be summed up as follows:
Given the diversity of capabilities of mobile web browsers, what kind of content should I serve to Googlebot-Mobile?
The answer lies in the User-agent that Googlebot-Mobile supplies when crawling. There are several User-agent strings in use by Googlebot-Mobile, all of which use this format:
[Phone name(s)] (compatible; Googlebot-Mobile/2.1; +http://www.google.com/bot.html)
Resources: http://googlewebmastercentral.blogspot.com/2011/02/making-websites-mobile-friendly.html