During one of my first jobs working in software, I was responsible for working on the functionality that allowed the front-end to talk to the middle-ware asynchronously.
That sounds way fancier than it really is, right?
Basically, I was doing a lot of Ajax. Of course, at the time, it was really cool stuff because it was while Ajax was become more mainstream, and the product on which I was working was using Prototype, and had a lot of neat stuff going on.
But whenever you end up using a new technology, and they are supported in a variety of ways in different browsers, then you’re bound to have edge cases that your users catch that are not caught by you or your testing department.
And if you deeply care about the stuff on which you’re working, getting support tickets for the things on which you’ve worked can sometimes be a major downer.