We present the first analysis of the Join-the-Shortest-Queue (JSQ) routing policy for Web server farms. Web server farms involve a collection of Processor-Sharing (PS) servers, whereas prior analyses of JSQ have always assumed First-Come-First-Serve (FCFS) servers. This work introduces a new technique: Single-Queue-Approximation (SQA), and uses the technique to prove some interesting insensitivity properties for Web server farms. Based on joint work with: Varun Gupta, Karl Sigman, and Ward Whitt.