Many people host more than one mojoPortal site and upgrading all of their sites can become very complex and cumbersome. This article will shed some light on the ability to separate some of the web.config configuration settings into individual files.
Note: This is an advanced topic and use of the items discussed here are not beneficial for most mojoPortal installations. If you have several sites that you update on a regular basis, this document will be very beneficial.
configSource - The Key to Happiness
Okay, so a configuration option isn't really the key to happiness but this read more