You could try one of many different load testing suites available.
For example, here is one such package:
http://loaduiweb.org/[
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LoadUIWeb is a free desktop tool for performance, stress, scalability and load testing of web applications. Designed from the ground-up to help you focus on the tasks at hand, it does not require programming knowledge. It works with both traditional HTML web sites and with Rich Internet Applications using modern web technologies like AJAX, ASP.NET, Flash, Flex and Silverlight.