Java EE (Java Enterprise Edition) General Discussion

Hello guyz,
I need a clarification...
Im having a servlet which is supposed to handle request from a mobile device, and in the mobile device how i form the request manually by appending the form components values in the URL like im forming the url by appending
http://localhost/<servlet-name>?paramname1=paramvalu1&....etc

And in the servlet when im using doGet its working fine..Whn i change the doGet to doPost its says "The specified HTTP method is not allowed for the requested resource "

But it works fine for doGet.

Wats the problem??Why am i not getting with doPost...??
Also i wud b greatful if any one clearly explain me the difference between doGet and doPost i refd so many materials by there seems to be no clear descrimination.

Thank You.

Regds,
Gokul