Do not rely solely on your spell-checker, as the following illustrates:
I have a spelling chequer,
It came with my pea sea,
It plainly marks four my revue,
Miss steaks eye kin knot sea.
Eye strike a key an type a word,
And weight four it two say,
Weather eye am wrong oar write,
It shows me strait a weigh.
As soon as a mist ache is maid,
It nose bee fore to long,
And eye can put the error rite,
Its rare lea ever wrong.
Eye have run this poem threw it,
I am shore your pleased two no,
Its letter perfect awl the weigh,
My chequer tolled me sew.
(from Future Perfect website)