Web archiving is the practice of preserving websites as a historical record. It is a technologically-challenging endeavor that has as its goal the creation of a high-quality archived website that looks and behaves exactly like the original website. Despite the importance of the notion of quality, comprehensive definitions of Information Quality (IQ) in a web archive have yet to be developed. Currently, the field has no single, comprehensive theory that describes what is a high-quality or low-quality archived website. Furthermore, most of the research that has been conducted on web archives has been system-centered and not user-centered, leading to a dearth of information on how humans perceive web archives. This dissertation seeks to remedy this problem by presenting a user-centered grounded theory of IQ for web archives. It answers two research questions: 1) What is the definition of information quality (IQ) for web archives? and 2) How can IQ in a web archive be measured? The theory presented is grounded on data obtained from users of the Internet Archive's Archive-It system, the largest web-archiving subscription service in the United States. Also presented are mathematical definitions for each dimension of IQ, which can then be applied to measure the quality of a web archive.