For better user experience it is recommended to use Shariff_XH instead of this plugin.
It requires CMSimple_XH ≥ 1.5.4 and PHP ≥ 5.2.0
The latest changes are listed in the changelog. For further details you can read the manual online. You can see it in action (and use it ;-) in the header of this site.
If you have already installed at least version 1rc3, you can download and install the patch. This won't overwrite any config, language or css files.