Sometimes it's necessary to debug CMSimple_XH and the installed plugins, particularly if you're facing a blank browser window (so-called “White Screen of Death”). This can be done easily without changing any PHP scripts – not even FTP access is absolutely necessary.
To do so, just upload a file _XHdebug.txt to the configured downloads folder of your installation. The contents of this file have to be a single digit between 0 and 6 (the debug level). The meaning of this digit is given in the following list:
If the file is empty, debug level 1 is set. Since CMSimple_XH 1.5 there's already a file XHdebug.txt in the download folder. To activate debug mode you just have to rename this file (i.e. prepend an underscore to the name).
As soon as the file exists a message is shown in the back-end, that debug mode is enabled, and errors will be reported in the (X)HTML output directly below it. The debug output is only displayed in admin mode 1), but due to a bug some of it was actually shown to visitors in CMSimple_XH versions before 1.5.4, so it's best to turn debug mode off, when you've finished debugging.