When building a VS 2005 Web Site Project you experience very slow build times – where compilation seems to mysteriously pause for 30+ seconds (or even minutes), before continuing each time you do a build or F5 of the project.

This compilation performance slow-down might be the result of a problem I call “dueling assembly references”.  This can occur when you setup multiple “automatic refresh enabled” file-system assembly references within your web site project to multiple assemblies that in turn share common assembly dependencies whose version numbers are different.  The post below describes this in more detail and how to fix it.