HTTP Server

Hi,
    Can any one please help me to listout thee minimal requrements for HTTP Server /1.1 .As I am working on unix system please inform about the implentation related site (which is simple)so that I can go forward.

and
    How the GET and POST methods are implemented.
I tried to write one simple server(HTTP/1.0 withGET and HEAD methods),there when no filename is given i gave filename as some default html page.I am using mozilla/4.0 browser.Then the problem is instead of showing the html page .It is giving the window saying to download the file.If anyone knows the reason please write to me

Thanks