As Jamie said, it comes from Administration > Site Settings.
We have no such setting in the Web.config of the latest version of mojoPortal, we may have had a setting like that a long time ago, so if you really have that setting in your Web.config file it is likely that you are not using the latest version of mojoPortal.
You can find your version under Administration > System Information, the current latest version is 2.3.6.5.
Best,
Joe