This should (I think) be easy to identify: I was watching TV earlier on my 27" ProScan, a regular CRT, when all of a sudden I noticed a 1" horizontal line in the upper right quadrant. Depending on the background colors, it was either very visible (light colors) or hidden (black/blue/brown).
I switched channels and it was still there. But then I switched off and then back on the TV and the glitch was gone. I thought I had some kind of "burn in" issue, which is strange since I've had it since 1995 and don't use it for video games.