I am planning to write an application in windows which will temporarily block the configured websites irrespective of what browser I am using. As I am completely a newbie in this I want to know where to start. Please provide me with any useful links which can help me. If you know any similar opensource program, please share it with me so that I can get an idea of what to do.

As I am completely a newbie in this I want to know where to start.

I'd start by figuring out how a website might be blocked, regardless of which browser makes the request.

Please provide me with any useful links which can help me.

This link is probably the only one you need.