2 seconds after I checked in some work on a web page, co-worker runs to me, freaking out because "This is not how I wanted it to look!" and waving a printed mock-up in my face.

I inherited a shitty, bloated, broken, 10-year-old site with dumbass CSS, but I did my best to work with it. I'm not surprised it's broken, so calm the fuck down and let's talk about what you're seeing and I'll happily fix it. It will be okay!