Let me serve as an example to anyone changing their CSS files.
I was changing the colors in the blog’s CSS file when this happened. I clicked upload and closed the text editor. Then my FTP program spazzed out. It hadn’t uploaded the file, but it did wipe the previous one. No problem. I can open the one on my computer right? Yes I could, but I made a fatal mistake and it overwrote the file on my computer with the empty file from the server. Now I have to redo the work from this week. At least I had a backup from a week ago.
Lesson learned: Backup the CSS file before you start working on it.