This chapter discusses important elements that contribute to the usability of text-based products namely, legibility, readability, comprehensibility and accessibility. Out of these four, comprehensibility is most crucial in the creation of a positive user experience. Legibility concerns typographic issues such as font styles and sizes, line height and length, and the overall page design, as well as more technical aspects such as document formats, paper size and color, surface structures and ink qualities. Comprehensibility is an extensive area of research, which often concentrates on learner's skills and abilities. Reading is a cognitive process, and the amount of effort needed is affected by the legibility and readability of the text, as well as by the individual's personal cognitive traits. The usability of a text can be approached even more holistically by evaluating the accessibility of texts. Accessibility, then, is one further significant topic to be considered in the context of textual usability, and particularly the usability of translated texts.