The left hand column is a post I saw on the web. The right hand column is the result of running through my spell checker (which does some grammar checking). The results are marginally better.

Spelling checker checker

    

Spelling checker

    

I have a spelling checker.

    

I have a spelling checker.

    

It came with my PC.

    

It came with my PC.

    

It plane lee marks four my revue

    

It plane lee marks four my revue

    

Miss steaks aye can knot see.

    

Miss steaks aye can knot see.

    

Eye ran this poem threw it.

    

Eye ran this poem threw it.

    

Your sure real glad two no.

    

You're sure real glad two no.

    

Its very polished in its weigh,

    

Its very polished in its weigh,

    

My checker tolled me sew.

    

My checker tolled me sew.

    

A checker is a blessing.

    

A checker is a blessing.

    

It freeze yew lodes of thyme.

    

It freezes yew lodes of thyme.

    

It helps me right awl stiles two reed,

    

It helps me right awl stiles two reed,

    

And aides me when aye rime.

    

And aides me when aye rime.

    

Each frays come posed up on my screen

    

Each fray come posed up on my screen

    

Eye trussed too bee a joule.

    

Eye trussed too bee a joule.

    

The checker pours o'er every word

    

The checker pours o'er every word

    

To cheque sum spelling rule.

    

To check sum spelling rule.

    

Bee fore a veiling checkers

    

Bee fore a veiling checkers

    

Hour spelling mite decline,

    

Hour spelling mite decline,

    

And if we're laks oar have a laps,

    

And if we're lacks oar have a laps,

    

We wood bee maid too wine.

    

We wood bee maid too wine.

    

Butt now bee cause my spelling

    

Butt now bee cause my spelling

    

Is checked with such grate flare,

    

Is checked with such great flare,

    

There are know faults with in my cite,

    

There are know faults with in my cite,

    

Of nun eye am a wear.

    

Of nun eye is a wear.

    

Now spelling does not phase me,

    

Now spelling does not phase me,

    

It does knot bring a tier.

    

It does knot bring a tier.

    

My pay purrs awl due glad den

    

My pay purrs awl due glad den

    

With wrapped words fare as hear.

    

With wrapped words fare as hear.

    

To rite with care is quite a feet

    

To rite with care is quite a feet

    

Of witch won should be proud,

    

Of witch won should be proud,

    

And wee mussed dew the best wee can,

    

And wee mussed dew the best wee can,

    

Sew flaws are knot aloud.

    

Sew flaws are knot aloud.

    

Sow ewe can sea why aye dew prays

    

Sow ewe cans sea why aye dew prays

    

Such soft wear four pea seas,

    

Such soft wears four pea seas,

    

And why eye brake in two averse

    

And why eye brake in two averse

    

Buy righting want too please.

    

Buy righting want too please.