Often, our Rails apps will need to produce HTML and CSS. Unfortunately, we will not spend very much course time on these topics. Some students will be familiar with these technologies from past experiences.
Especially if you are not, it is quite important that you familiarize (or re-familiarize) yourself with them since our coverage in class will be fast paced.
Complete the Codecademy HTML & CSS course
(Optional) Read through LearnLayout to better understand how to do layout with CSS.
(Treehouse has some additional material that you can check out, though it goes into more depth than I'd expect you to work through on your own.)
This class is primarily concerned with data flow and functionality over design, so a little bit of extra CSS experience can really help you stand out and make your projects look significantly more polished.