The accepted wisdom of website performance testing used to be that you would record "realistic" scenarios
and repeat them with n virtual users to determine whether the back end could keep up.
Web application performance testing, however, requires most of the testing effort to be directed
at the front-end. Testing and reconfiguring the back-end usually results in savings in the 10s of milliseconds
in page delivery time, whereas optimising the front-end easily saves seconds for the end-user.
When an end-user is working with a web application, 80-95% of the wait time for each operation is determined
by what is happening in their browser or across the network, rather than the server or database. If you deliver a
slow front-end, it will be slow whether you have 2 users or 2,000.
Yahoo Developer Network: Exceptional Performance
Fiddler - allows you to monitor and alter network traffic