Empresa activa
From a user clicking a link on a web page, describe the process and events that occur from start to finish (both client and server side).
Anónimo
I wrote a detailed roadmap to figure out how to answer properly this question: http://42opinioes.blogspot.com.br/2013/03/what-happens-when-you-click-on-submit.html. Basically, you should explain how HTTP over TCP/IP suite works. I think it is not necessary explain how browser interact with OS to accomplish this task.