I have recently gotten a web application from a nasty contractor who claimed to be a good expert in programming. Unfortunately, we believed him. Functional of the web application seemed to work okay at first glance. However, once the client started using application in the real conditions the things went bad. The contractor has gone after a payment, and I have gotten his errors to fix for a client.
I decided to document a few errors that I found along the way. These are errors that every good programmer should already know to avoid… but obviously some people need to be reminded about them.