This document reviews CSS (Cascading Style Sheets) concepts covered in Week 11. CSS is used to control the presentation and styling of HTML documents. There are different types of CSS selectors including element selectors for HTML tags, class selectors that can be applied to any element, and ID selectors that uniquely identify a single element. Styles can be applied via embedded, linked, or inline styles. Linked style sheets allow controlling the presentation of an entire website from one external CSS file.