Error messages are common in the system logs -- in fact, your operating system as a whole is nothing more than a bunch of errors occurring that the operating system handles gracefully.
Click on an icon? That's an error (more specifically, an "interrupt") that interrupted whatever the operating system was doing at the time, and the operating system handles it gracefully by highlighting the icon you clicked on, then happily continues doing what it was doing before.
The short and skinny of it is that if you don't know what those messages mean, and if there's nothing seemingly wrong with your computer, then diving into the world of operating system log files is only going to make you paranoid. Just because something says "error" or "access denied" does not mean that anything is wrong with your computer.