You must try to make sure that your work has as few mistakes in it as possible. Most programs now come with spell checking built in, but this only proves that the words are in the dictionary, not that they are the correct words for your sentance. You will still need to read your work carefully to spot any mistakes. Try reading this poem out loud.

Eye have a spelling chequer
Witch came with my Pea See
And plainly marques fore my revue
Mistakes I mite knot sea.

I’ve run this poem threw it;
I’m shore your pleased too no
Its letter perfect in it’s weigh:
My chequer tolled me sew.

Sew to my ant I scent this rime
Too sea watt she wood say
But I am still hear weighting
Well the thyme has past aweigh.

Proof read your work, the computer can’t spot everything.