I have been trying to be better about leaving programs running on the computer. As in, actually closing them, so that I can turn the computer off at night, or at least put it in sleep mode. As a result, I sometimes have to "resize" some programs when I turn them back on.
So when I started Mozilla Firefox today, I noticed that it looked weird. I was racking my brains, trying to figure it out, but I couldn't! So I was looking all over the place, trying to find what was missing. Then I went to my 2nd FF window, and that's when I noticed what was missing: the other tabs.
Yes, I had only 1 tab open and so I thought it looked like it was missing something important.