It was the time of the 90s when one created HTML with frames. During an HTML exam we had 1 hour to create a website with 3 frames. Top, left, main. Some aligned random images and some formatted text. Kind of boring, I know. So I finished early and handed in my diskette with my homepage. To make it easy for him I added my name and class to the title.
When we got our grades I was in for a surprise since I had expected a good grade. I asked him why I didn't get a good grade. He kind of shouted at me that my task was perfectly done but I shouldn't have written my name in the title but name and address of this school. It is not a really dramatic thing but I always hated when teachers quietly assumed stuff and didn't tell us. And then handed out bad graded for totally unrelated stuff.