Web Design is a bit of a dated term in so much as it covers a lot of different areas, each a speciality in it's own right. The design of a website incorporates UX (user experience), UI (user interface), IA (information architecture), Content Strategy and is brought together with Front End Development.
In regards to physically designing a website then the basics of design will always apply; Layout, Typography and Colour. Knowledge of HTML and CSS is a requirement if you really want to understand how a sketch or digital design can actually translate into a flexible, useable website.
Design is ultimately about problem solving no matter what the medium.