I noticed almost all of StackExchange's sites uses the same url in mobile browser, I think this is cool because when I share something on my phone, people viewing the link would not see a mobile webpage on their desktop. What is this specification called by W3C? How do I find other websites that use this technology. I noticed that ArsTechnica and the Telegraph used the same url with their desktop version.
closed as not a real question by toomanyairmiles, John Conde♦ Jun 2 '12 at 17:25
It's difficult to tell what is being asked here. This question is ambiguous, vague, incomplete, overly broad, or rhetorical and cannot be reasonably answered in its current form. For help clarifying this question so that it can be reopened, see the FAQ.
Looking at http://webmasters.stackexchange.com/ I see that it has a specific design for the iPhone, different from the design shown to desktop browsers. It's because the site detects the browser's user agent and serves html/css accordingly.
To know more about the browser's user agent you can read the wikipedia article http://en.wikipedia.org/wiki/User_agent
If you use the Safari browser, you can change the browser's user agent from the menu and check how a specific site behaves for Apple mobiles.