Unless you’re so poor at spelling or English in general that a spell-checker wouldn’t do you much good anyway, there isn’t really any excuse for this sort of thing:

For heaven's sake, use a spell-checker!

Did you spot the two errors? I especially liked the rendering of the word ‘intelligent’!

But just think: it was not only the person who wrote this who failed to notice the spelling mistakes. So too did the person who signed it off to be printed, and so too did the person who printed it.

Of course, the spell-checker won’t pick up words which are incorrect in the context, but correct in themselves. This fact is exemplified in the following poem. There are several versions of this. I obtained this one from the Louisiana Tech University website.

A Little Poem Regarding Computer Spell Checkers...

Eye halve a spelling chequer
It came with my pea sea
It plainly marques four my revue
Miss steaks eye kin knot sea.

Eye strike a key and 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 two 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.