Configuring IIS WebSpeed is done by editting text files named
IISWebSpeed.config. There is a configuration file located in the install directory. This file defines the root configuration which is inherited into all websites that have the module enabled.
IIS WebSpeed will also check for a files named IISWebSpeed.config in the root of websites that have the IIS WebSpeed module enabled for website-specific configuration. The website specific configuration will inherit the root settings. You can disable IIS WebSpeed for a website by renaming IISWebSpeed.config to something else.
PageSpeed Configuration and Tuning
Recommended reading for setting up PageSpeed optimization in detail