The Invisible Visible

My dear friends, a new riddle and a new challenge awaits. Post your best guesses for the answers in the comments.

You just saw me, but you think you saw whatever you were looking at.
Try to see me and you’ll fail. You’ll just see whatever you’re looking at.
By the time you turn your head to see me, I’m no longer there anyway.
What am I?

Note: Official riddle answer: Increased Visibility