Sharing of data in collaborative environments requires mechanisms that ensure the consistency of data in spite of concurrency and failures. This is traditionally handled by transactions or extended transaction mechanisms. The World Wide Web, although originally designed as an information storage and retrieval system, is being extended to serve as a vehicle for collaboration. However, the proposed extensions mainly address the basic issues such as file formats and up- and downloading of files. We are developing a configurable set of services for handling concurrency, recovery and collaboration that can be integrated into different system environments. We show an approach to use them for supporting cooperative work on the Web. In particular, the design and implementation of a cooperative concurrency control mechanism for the Web is presented.