Just a quick reference to very good materials for people, who gets confused about responsive design, fixed grid system and fluid grid system. For beginners rather than for professionals.
Plus some interesting jsFiddles, extracted from mentioned answer for:
- fluid non-responsive layout,
- fluid responsive layout,
- fixed non-responsive layout,
- fixed responsive layout.
These fiddles are, on contrary, completely Bootstrap-free, based on pure CSS media queries, which makes them a good starting point, if you would consider similar solution without using Twitter Bootstrap.