Internal Server Error? Why is this happening?
Q. Why is this happening?

This can happen if the .htaccess files in your Drupal directory use settings or trigger actions which are not supported by your Apache server config. If you're not running the server yourself, but are registered with a webhost, you can either ask your webhost to enable the options in question, or just comment them out in the htaccess files.


The options which are known to cause an Error 500 are:

Options -Indexes
It may also occur when setting very permissive file permissions (777) and your hoster added some security checks to avoid this. Try to lower permissions.
Another problem can occur if you're using .htaccess files using UTF-8 codification with Byte-Order Mark (BOM). Reencode your .htaccess files properly without BOM to solve this.
This error can also manifests itself as a PHP error. Try adding the code below to one of your PHP files such as local.php, then checking the error log file it generates.

ini_set('log_errors', 1);
ini_set('error_log', 'errorlog.txt');


Read:

HTTP Error 500 Internal server error

List of HTTP status codes