Responsive design based on existing website code

We currently have a div based website that runs on a CMS platform that we would like to have the theme/wrapper(top,left,footer) modified with as little customization to the actual html code base, to have the website be responsive. You will be free to add new div/html/html5 blocks, css, css3 and java script as needed. We already have mockups ready for each screen size mobile and tablet. You should: a) Already know how to create a responsive design from scratch b) Have sample websites to show us and be able to explain your responsive code c) Before the project is won you'll be asked to do a proof of concept for one simple page from the website. All winners will be given a $20 just to do the proof of concept with the winner being given the full value of his/her bid to complete the project. d) Proof of concept should be created before the end of the weekend Tools to be used: Jquery, modernizer, css3 etc