A good eye for design is another important skill. Regardless of the content, no web surfer will stay long on a website with messy layouts, clashing colours, difficult to read fonts and humdrum images.
As you'd expect audience empathy is key. Bright, bold designs that works for one audience might be an instant turn-off for another. Equally, delivering a straight-to-the-point, business-like format might not be lively enough for some.
You'll need to visualise the complete site experience. Once the design is in your head, or sketched out, it's easier to harness the tools and languages and bring it to life.
Many designers prefer to create the layouts with advanced graphical-interface editors. Such a tool allows them to focus on the visual layout and flow aspects of the design, without getting bogged down in HTML or CSS specifics.
Adobe's range of tools are a firm favourite with many designers, even though the price may be prohibitive to some. However, there's plenty of free and open source alternatives, so give them a try and you'll learn a great deal about the mechanics and nuances of website design in the process.
Remember design is an ongoing process. Whether it's new ideas, audience feedback or interoperability with the latest techniques and technologies, there's always room for improvement and subtle refinement.