You can now find our patterns & practices Performance Testing Guidance for Web Applications on MSDN in HTML. It's the same guidance we hosted on CodePlex. CodePlex was our channel for agile release of the guidance. Once we baked the guidance, we ported it to MSDN. For some customers, MSDN is a trusted source, so being on MSDN is important. Additionally, MSDN provides some additional hooks and channels.
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You can download the patterns & practices Performance Testing Guidance for Web Applications from CodePlex.