There have been some great articles recently on A List Apart, especially this one (which also defines the word “grok”). A lot of what author Craig Cook says here echoes my philosophy toward designing. It’s important for your code to be as standards-compliant for myriad reasons, outlined in that article, as well as this other article.
But Cook’s piece here really touches more broadly on what I’ve learned as a designer: a designer (web or print) must be a writer, engineer, and artist, and in that order. If any of these elements are lacking, then the end result will be at least partially unrealized. The key here is that each of these disciplines is distinct in the way it goes about creatively problem-solving. The message must come first. The way the design is put together must be functional for the end viewer. And finally it must be visually appealing. These principles are universal to any medium.