This wiki is for Moodle 2.4. For up-to-date documentation on the latest stable version of Moodle, see Moodle Docs 2.5.
Coding errors (or coding_exceptions) are problems that are probably caused by incorrect code. For example a plugin that does not communicate correctly with Moodle core.
These errors are normally not caused by incorrect user input or temporary problems like the connection to the database server being down.
As with all error messages, it's a good idea to search moodle.org and the tracker to see if anyone else has reported the problem.