A list of useful project management rules for web development companies and digital agencies could be a mile long. But what good is a list that doesn't help you remember the truly immutable rules? You know: the ones that you shouldn't be ignoring, bending, twisting, breaking. In this article we give you the rules that we use in our digital agency and the exact explanation how they help us manage our web development projects better. We also mention what happens when you go around these rules. This presentation is based on our blog post: https://www.simpfinity.com/blog/tiny-list-pm-rules/