500 Error Joomla

The most likely cause for a 500 error while using Joomla is the amount of memory allocated to php applications. To resolve this you create a php.ini file, which you can add to the related configuration folder in the /etc directory on linux hosts, or you can add the file directly to the directory where the php application is located.

In the php.ini file add:

memory_limit:40M
register_globals = 'off'

The registered globals option is a security feature that decreases the potential for nasty things to happen. Albeit the potential is practically miniscule, but turning registered globals off reduces risk even further.