Problems that reading can prevent:

Patron: "Hi, my son accidentally logged off of his computer as soon as he got on."

Me: "I'm sorry, the only thing you can do is just sign him up again." (There is a 1.5 hour wait).

Patron, her face becoming cumulonimbus: "WHAT!  That is not fair, he just made a mistake!  That's not right!"

Me: "When you click "done" on the computer, a message pops up that says, "Are you sure you want to end your session?"  You have to click "yes" on that before you end your turn.

Patron, becoming more incensed: "HOW CAN YOU HAVE A SYSTEM THAT DOES THIS TO PEOPLE?  HE JUST MADE A MISTAKE!  THIS IS NOT FAIR!"

Me, resisting the urge to perform a massive facepalm: "If you make a mistake and accidentally push "done" on the computer, then another message pops up that asks you if you're sure you are done.  Only if you push "yes" will it close your session.  If you read the message and push "no" because you realized you made a mistake then your session won't end.

Patron: "I CAN'T BELIEVE THIS!  HE JUST MADE A MISTAKE!"

I shrug because I don't know what else I can tell her, and I'm getting mad because she is blaming me for the fact that her son made this dumb mistake.

Patron: "IS THE MANAGER HERE? CAN I SPEAK TO THE MANAGER?!"