This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Variant: This element is less frequently specified. It is used for creating locales with vendor- or browser-specific code. Examples are WIN for Windows, MAC for Macintosh, and POSIX for POSIX (Linux or UNIX).
Does this mean, user should hope that they will get very specific language if they set language in browser very precisely (providing even the OS in locale), and so they should follow certain guidelines?