The advantages of computer-assisted grammar teaching and more recently, web-based grammar teaching, include the possibility, for the instructor, of devoting class time to teaching communication skills, and the capacity of individualizing the course work. Several websites have been created for these very reasons. However, most of these sites include only a small portion of the grammar and very few are based on educational principles. This paper will summarize what should be the guiding principles in the design of this type of website, most of which involve instructional design and the need for structure and adaptability to different learning styles. It should also be noted that there are design principles specific to grammar teaching, such as the distinction between exploratory and pre-established modes, and the scaffolding of concepts. The application of these principles will be illustrated through the presentation of a web site.