Most implementationsof HTTP servers do not distinguish among requests to differeut pages.This has the implicatiou that requests for popular pages have the tendency to overwhelm the requests for other pages.In addition, HTTP servers do not allow a site to specify policies for server resource allocation.This paper presents a notion of wality of service that enables a site to customize how an HTTP server should respond to external requests by setting priorities among page requests and allocating server resources.It also describes a design and an implementation of a distributed HTTP server, QoS Web Server, that enforces the quality of service constraints.The performance aualysis of the prototype server indicates that the server provides the desired quality of service with minimal overhead.