You are neither graphic nor ergonomist and you still want to make a website or web application with a mobile version which is not too bad and such without you smash head? Several projects exist to make your life easier. Y'll need of course to have some understanding of HTML or you will very quickly break your teeth. Each of the frameworks I'll talk about is popular, maintained, scalable, documented and above all free and open source, so you can enjoy your community improvements or make your own version in a separate branch. These frameworks also have a rather strong dependence with HTML5 and CSS3.
When I told you it was all baked, I lied a little, because if you use a CSS quite ready, your site / application will look like or even be the same as your neighbor. To avoid this it is possible to customize your version of the framework, in bootstrap there is an interface to change the colors and set some parameters. For Foundation, there is also a much simpler interface to get to the point.
Both frameworks are in pretty much the same thing, the only real change will be at the level of classes that you will use. For my part I have used both and I must admit a slight preference for Bootstrap.
You will find all the necessary references to start here: