This section is for general developer and administrator questions that commonly come up and their answers - particularly questions that don't really fit under any of the other existing topics. Please list one question per sub-page and follow the format of the first question about Drupal Sites on OIT Web Hosting Unable to Send Emails.
If you need some generic advice about how to deal with a Drupal site that has stopped working (e.g. the dreaded "white screen of death"), Kevin Pittman has written a fairly comprehensive guide called "So, You Blew Up Your Drupal 8 Site - Now What?". It's written for Drupal 8, but all of the concepts apply to earlier and later versions – the specific details will just be a little different.