This parameter controls whether URLs from the Microsoft IIS web server should be lowercased. IIS is case insensitive, so converting all URLs to lowercase before requesting them may result in less duplicate content being downloaded.
In some cases it is not desirable to lowercase URLs from an IIS server, as there may be an application or CMS (Content Management System) running on the server which is case sensitive, in which case lowercasing the URLs will result in "Not Found" errors.
The default setting for this parameter is false i.e. don’t lowercase the URLs.