Debugging HTTP Requests with Fiddler
If you don't have it yet, you can download and install Fiddler Web Debugger from http://www.fiddler2.com. It is a free tool that simplifies the process of debugging HTTP requests. It is a Web Debugging Proxy that configures itself in such a way that all HTTP requests from WinINet (Windows Internet application programming interface) flow through Fiddler before reaching the target web servers. Likewise, all HTTP responses flow through Fiddler before being returned to the client web browser and the Silverlight RIA. Fiddler logs the requests and the responses, and therefore allows us to understand the underlying communications.
In this case, we will use Fiddler to debug HTTP requests and responses for SharePoint ...