Qwerty keyboards were created to slow down the typing (and to split apart the letters often used consecutively).
Christopher Latham Sholes designed the QWERTY in 1868. He arranged the letters to slow the typists down and to prevent typebars from clashing and thus jamming the typewriter.
Keys were laid out this way in order to prevent the most used letters from being typed with the middle fingers and to force common pairs of letters to be typed with different fingers or hands.
According to the language of the user, the layout and both finger and hand uses were accounted for to prevent the jamming of the typebars.
Keyboards are the only computer component that remained the same since 1878.
Wikipedia.org – Typewriter
Earthlink.net – Consider Qwerty
bcgsc.ca – Carpalx
the keys are also arranged so that salesmen could easily type the word “TYPEWRITER” – all it's letters are on the top row.
@ethelaardvaark: when you've done, space become %20 who are URL Encoding. Refresh the page and %20 became space :)
I will correct it in next release.
An interesting aside: placement of more frequently used characters remain on the left side because the return bar/key was situated to accommodate right-handedness.