It all started with the Wireless Application Protocol, better known as WAP.
WAP is a result of continuous work to define an industry wide standard for
developing applications over wireless communication networks.
The WAP Forum, originally founded by Ericsson, Motorola,
Nokia, and Unwired Planet WML was formed to create the global wireless protocol specification that works across differing wireless network technology types, for adoption by appropriate industry standards bodies.
WML (Wireless Markup Language) is a markup language based on XML,
and is intended for use in specifying content and user interface for narrowband devices, including cellular phones and pagers. WML is designed with the constraints of small narrowband devices in mind.
These constraints include: