This is not really a joke, but it's kinda fun
Mental Eye Test
Test your eyes
Quickly count every "F" in the following text:
FINISHED FILES ARE THE RE
SULT OF YEARS OF SCIENTI
FIC STUDY COMBINED WITH
THE EXPERIENCE OF YEARS...
(SEE BELOW)
HOW MANY ?
................. 3?
WRONG, THERE ARE 6 -- no joke.
READ IT AGAIN !
The reasoning behind is further down.
!
The brain has difficulty processing the combination "OF".
Incredible or what? Go back and look again!!
Anyone who counts all 6 "F's" on the first go is a genius.
Three is normal, four is quite rare.
Anyways i did count all 6

How did you do ?