I checked in a bugfix that I implemented using client-side code, since a checkbox was disabling a field but not clearing it out.
The tester gets back to me, and claims my fix doesn't work.
They said, "What's a browser cache?"
I had to explain to a senior testing lead who's ten years my junior and paid at least ten grand more than me how to clear IE's cache.
"I appreciate SDF but it's a general-purpose server and the name doesn't make it obvious that it's about art." - Eugen Rochko