Mobile Devices such as cell phones with web access and Personal Digital Assistants (PDA's) are becoming more common. The infrastructure that supports "Wireless web " is becoming larger and more reliable with the advent of time. There is clear indication that mobile users would keep on growing at tremendous rate. In this scenario, there are good opportunities for developing web pages special to these mobile devices, so that they can make a good use of technology. However, this idea is not liked by many developers. The main reason being the cost of adding extra pages to their web site. Especially, if we look at cellular phones, they use a different standard called "Wireless Markup Language " (WML) for consuming web pages. And we know that developing WML pages would take extra effort on developer's side and hence more cost.

http://www.beansoftware.com/ASP.NET-Tutorials/WML-Mobile-PDA.aspx