There are many mapping schemes proposed in previous research on parallel proxy servers. The operations of these schemes are mainly URL-based, and therefore cannot fully benefit from the new persistent connection feature of HTTP/1.1. In this paper, we propose a site-based mapping scheme that forwards all requests targeting on the same web site to the same proxy server. The scheme then allows the proxy to use a single persistent connection to serve many client requests. The major advantage of the scheme is the reduction in the number of connection establishments. This reduction can save network bandwidth and reduce the user-experienced latency. Simulation results show that the proposed site-based scheme reduces 40%-70% of the connection setups and teardowns when compared to a traditional URL-based mapping scheme.