If you can successfully process text with Diacritic marks, you are likely using either iso-8859-1, or its close cousin, windows-1252. There is no polite way to put this, so if you are running on a Microsoft platform, or cut and paste from documents produced by Microsoft software, or even allow comments to be posted by people who might be doing one of the above, you need to be aware of the 27 differences, summarized by the table below: