The Stone Steps version of the Webalizer is able to use language files to produce the reports and progress messages. The Webalizer GUI is searching in the subdirectory 'lang' of the Webalizer directory for these language files and is presenting the available languages in this list view.
Cave: Selecting a language in this list view only changes the language of the generated HTML report. The language of the GUI can be changed on the 'GUI Options' page.
If you use any language other than English, you have to make sure that the HTML Charset matches the selected language.