GSM shield with Arduino Mega

I really need a help here, any help would be great.

I'm using GSM shield with Arduino mega. I want arduino to respond to any particular message received from website.

The question is how do i make such website from where user can ask information from arduino. How do i configure arduino as a server to respond to website. if arduino is server than what else i need to have regarding the website through which information is required.

Making a website involves buying a domain name, hosting service, and thenusing HTML or a website builder to get what you want. A lot of work, and not really a question to be answered on an Arduino forum.