Internal Server Error 500 when trying to install JCE 2.2.6 in Joomla 2.5

When trying to install the JCE content editor for Joomla version 2.2.6 in Joomla 2.5 it failed with HTTP Error 500 Internal Server Error. Directory permissions was not a problem and there was no problem installing other extensions. 

Solution: 

1. Download the JCE 2.2.6 zip archive to your computer.
2. Unzip it to a local folder, called for example "jce"
3. Upload the folder to your Joomla! tmp directory
4. In the Joomla! backend, go to Extensions -> Manage extensions and go to the box for installation from a folder on the server.
5. Enter the path where the uploaded folder containing JCE is uploaded, i.e. probably something like /var/www/mysitename/web/tmp/jce and click install.