Occasionally when I hit a bunch of keys while trying to find those elusive Windows/Visual Studio short-cuts I end up managing to spin the desktop on my PC so that it is either upside down or rotated by 90 degrees. I’m sure this is a useful feature if you want to fix your monitor to a wall or ceiling, but for most users it’s just an annoyance that is hard to get out of if you happen to do it by mistake… unless you’re good at Googling while in the handstand position.
So, if you’re reading this with your head tilted to one side, or indeed in an upside down position, the keys you need to press to get your desktop the right way up again are:
CTRL + ALT + Up Arrow
Using the other arrow keys will rotate your desktop back to less readable configurations.