Configuring IIS WebSpeed is done by editting text files named iispeed.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 iispeed.config in the root of websites that have the iispeed 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 iispeed.config to something else.

PageSpeed Configuration and Tuning

Recommended reading for setting up PageSpeed optimization in detail