We instinctively respond to design; colors, shapes, symmetry. And most people do pay attention to “what looks nice.” But design is much more than pretty patterns and witty layouts. It’s a centrally critical part of your site. It also functions on many deep levels that are not easily apparent.
Structure is a key component of design (indeed, it could be considered as its own science and design). It allows us to make sense of vast amounts of data and we’d be lost without it. A well-structured site makes a successful site 🙂