This option controls whether URL characters will be converted to lower case or not.
Unlike most Unix systems, Windows preserves character case in file names, but ignores differences in case when working with files. As a result of this, an URL requesting a file named Default.html and an URL requesting a file named default.html will return the same file. Since URLs are explicitly case-sensitive [RFC 2616; 3.2.3], Webalizer will treat these two requests as if two different files were requested.
If the 'Convert URLs to Lower Case' option is set, the Stone Steps version of the Webalizer will convert the entire URL, including the query portion of the URL, to lower case when processing IIS and Apache custom log files.
Please note: Only the Stone Steps version of the Webalizer is able to convert URLs to lower case.