Text is not an afterthought in the design process. It should be your first consideration. Readability should be one of the top concerns when it comes to any design project. If text can’t be read, then why are you designing in the first place? Good design delivers content in a way that is understandable; readability is a big part of comprehension.

The ultimate accomplishment for programmers is creating software that never breaks; but programming that doesn’t account for extreme situations is likely to do exactly that under those extreme circumstances. So programmers are trained to treat every case equally, whether it represents one user or one thousand.

The Elements of User Design by Jesse James Garrette