I never knew that!

I was listening to Radio 1 today and in 'Rage Against The Answer Machine' someone commented on how ridiculous people look when they pull into a service station and park by a pump only to discover the fuel cap is on the wrong side so they are forced to move their car so they can reach the fuel pump..
There was talk of situations when others have experienced this. This has happened to me and is quite embarrassing as other people sit in their cars and watch you making a fool of yourself.

What I didn't know or hadn't noticed is that on your fuel gauge there is a little arrow that points out which side your fuel cap is on.
I looked at my dashboard and sure enough there was the arrow as clear as day.
How have I not noticed this before?