how to capture http packet and save them as web page?

Well, you're going to need WinPcap[^] first, then you're going to need a managed wrapper library to make it easier to use in C#, like SharpPcap[^]

Then you're going to write code to capture packets, filter out what you need, process the results, format some data into a usable form, then display them in a web page.

Exactly how to do that depends entirely on you and what you want to do in this application so it's impossible to be more exact than this.

Have a nice day!