There are a plethora of free frameworks available that aim to aid in the rapid prototyping and building of responsive websites. The two most common examples being Bootstrap (http://getbootstrap.com/) and Foundation (http://foundation.zurb.com/). While they are great projects, particularly for learning how to build responsive visual patterns, I think they should be avoided in production.

I've spoken to plenty of developers who start all projects with one of these frameworks and then amend them to fit their needs. This approach can be incredibly advantageous for rapid prototyping (for example, to illustrate some interaction to clients) but I think it's the wrong thing to do for projects you intend to take through to production.

Firstly, from a technical perspective, it's likely that starting with a framework will result in your project having more code than it actually needs. Secondly, from an aesthetic perspective, due to the popularity of these frameworks...