Wireless Markup Language(WML)

Wireless Markup Language, based on XML, is a markup language intended for devices that implement the Wireless Application Protocol (WAP) specification, such as mobile phones, and preceded the use of other markup languages now used with WAP, such as XHTML and even standard HTML (which are gaining in popularity as processing power in mobile devices increases).

WML markup
<?xml version="1.0"?>
<!DOCTYPE wml PUBLIC "-//WAPFORUM//DTD WML 1.1//EN"
"http://www.wapforum.org/DTD/wml_1.1.xml" >
<wml>
<card id="main" title="First Card">
<p mode="wrap">This is a sample WML page.</p>
</card>
</wml>

Wireless Markup Language is a lot like HTML (Hyper Text Markup Language) in that it provides navigational support, data input, hyperlinks, text and image presentation, and forms. A WML document is known as a “deck”. Data in the deck is structured into one or more “cards” (pages) – each of which represents a single interaction with the user. The introduction of the terms "deck" and "card" into the internet and mobile phone communities was a result of the user interface software and its interaction with wireless communications services having to comply with the requirements of the laws of two or more nations.

WML decks are stored on an ordinary web server trivially configured to serve the text/vnd.wap.wml MIME type in addition to plain HTML and variants. The WML cards when requested by a device are accessed by a bridge WAP gateway, which sits between mobile devices and the World Wide Web, passing pages from one to the other much like a proxy. The gateways radio the WML pages in a form suitable for mobile device reception. This process is hidden from the phone, so it may access the page in the same way as a browser accesses HTML, using a URL (for example, http://example.com/foo.wml), provided the mobile phone operator has not specifically locked the phone to prevent access of user-specified URLs.

Reference : http://en.wikipedia.org/wiki/Wireless_Markup_Language