I'd been with the company for maybe two weeks, pushed some changes and updates to a client's site on a Friday afternoon as instructed by my boss, checked everything over and it's all fine.

Come Monday morning and this client is seriously miffed, not all of the changes had applied and the site was a mess all weekend. Turns out a bug with the caching plugin meant what we were getting in the office was different to outside.

Meetings were held and a new QA procedure was put in place.