Web archives play an important role in documenting history and enabling research using internet sources. There has been a short history of web archiving over the last 12-14 years, starting with individual efforts and evolving to established national archives. While web archives aim to preserve online content, what is archived may differ from the original live web pages due to technical limitations. Cooperation across archives is needed to address these challenges and better support scholarly research, such as through a proposed European research infrastructure called RESAW to integrate existing national archives.