This is an old chestnut but it bears repeating over and over again. Great websites are often laid low by poor typography. Organizations spend outrageous sums of money on original, thoughtful content, and make it almost useless with poor presentation. In my opinion, one of the most important points is made in a follow-up post (the original post predictably stirred up quite a bit of controversy).
Typography in practice is not choosing fonts or making fonts, it’s about shaping text for optimal user experience.
It’s things like grids, whitespace, line-height, sizing, and hierarchy—things that most people don’t consider—that make good websites great.
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For an additional treat, resize the Information Architects site in your browser and watch what happens when the window gets narrower. That’s really, really nice design.