Drupal Theme Editing: Locked Out from Admin with White Screen of Death

When you are busy editing or creating themes it is not difficult to find yourself locked out of your own system. This can happen for a variety of programming errors. When this happens (not 'should this happen' because as sure as eggs is eggs, it will happen sooner or later), firstly rename the theme folder you are working on. For example, if your theme is called beezee, then try:

$ cd sites/all/themes
mv beezee beezee_

This should get at least the user part of your website back in action, but you should try to load the admin part of the site. If you get the dreaded White Screen of Death (WSOD) then you need to clear the cache using the following command in the MySQL command interpreter
mysql> USE {database name};
Database changed
mysql> DELETE FROM cache;
Query OK, 3 rows affected (0.00 sec)
mysql> quit;
bye

Bingo! Your system is back and you can continue on your merry way.