Build New Web Technology

How hard it could be to build a very basic and simple new web technology like rails or asp.net --based on programming language that already exist -C , Ruby, c# .. whatever -, I've tried to type every line of code of rails as it is open source but it seems too big and complicated .. I'm tring to find to smallest amount of files and code to just get started and build on that later .. so if anyone can help that would be great -- maybe point to tutorial or reference or anywhere that could help me getting started on this -- Thanks