C64 common problems and how to fix it

To the original author:
I’m just preserving your valuable information. Just in case it would ever go offline.
As always I would like to refer to the ORIGINAL source here:

Check it out guys: http://derbian.webs.com/c64diag/

BTW: I’m using the most interesting and common errors, because some aren’t c64 related, but user errors. 🙂