http://translator.dictionary.com/text.html
Trying to see which of the most common English words get
translated to French then back to English correctly:

"WORD"=count
Original English text containing the word.  (in English)
  Translation to French.  (en frangais)
    Translation back to English. (Judgement.)   (in English sometimes)

"THE"=109975
The sun is bright.
  Le soleil est lumineux.
    The sun is luminous. (Correct.)

"TO"=58931
I went to the store.
  Je suis alli ` la mimoire. (Wrong already.)
    I am alli ` the mimoire. (Garbage.)
To live is not merely to breathe, it is to act.
  Vivre n'est pas simplement de respirer, il est d'agir.
    To live is not simply to breathe, it is to act. (Correct.)
It will cease to exist.
  Il cessera d'exister.
    It will cease existing. (No longer contains target word.)
Click here to shop the Bartleby Bookstore.
  Cliquetez ici pour faire des emplettes la librairie de Bartleby.
    Click here to make emplettes the bookshop of Bartleby. (?)
It will come to pass.
  Il viendra pour passer.
    It will come to pass. (Exactly correct.)
This computer belongs to me.
  Cet ordinateur appartient ` moi. (Wrong already.)
    This computer belongs ` me. (Wrong.)
This project is intended to supply petroleum to industry.
  Ce projet est destini pour fournir le pitrole ` l'industrie. (Wrong already.)
  This project is destini to provide the pitrole ` industry. (Wrong.)
With respect to the English language, spelling is important.
  En ce qui concerne l'anglais, l'orthographe est importante.
    With regard to English, the orthography is significant. (Close enough.)
English contains idiomatic combinations peculiar to it.
  L'anglais contient des combinaisons idiomatiques particulihres ` lui. (Wrong already.)
    English contains combinations idiomatic particulihres ` him. (Wrong.)
The words are arranged according to the ideas which they express.
  Les mots sont arrangis selon les idies qu'ils expriment.
    The words are arrangis according to idies that they express. (Close.)
The music is played according to the page each is on.
  La musique est jouie selon la page que chacune est allumie.
    The music is enjoyed according to the page that each one is allumy. (Almost.)
The music is performed according to the page in the book.
  La musique est exicutie selon la page dans le livre.
    The music is exicutie according to the page in the book. (Almost.)
The music is ruined according to the page in the book.
  La musique est ruinie selon la page dans le livre.
    The music is ruinie according to the page in the book. (Almost.)
The food is eaten according to the page in the menu.
  La nourriture est mangie selon la page dans le menu.
    Food is mangie according to the page in the menu. (Trashed elsewhere.)
(I give up, the idiots win:)
The music is enjoyed according to the page in the menu.
  La musique est appriciie selon la page dans le menu.
    The music is appriciie according to the page in the menu. (Trashed elsewhere.)
(:The idiots have destroyed themselves with utter stupidity!!)
The purpose of a dictionary is simply to explain the meaning of words.
  Le but d'un dictionnaire est simplement d'expliquer la signification des mots.
    The goal of a dictionary is simply to explain the significance of the words. (Wrong elsewhere.)
It professes to furnish the solution.
  Il professe pour fournir la solution.
    It professes to provide the solution. (Correct.)
I want to find the word.
  Je veux trouver le mot.
    I want to find the word.

"AND"=50120
Jack and Jill went up the hill.
  Jack et Jill ont monti la colline.
    Jack and Jill have monti the hill. (Wrong elsewhere.)
Jack and Jill want to find the word.
  Jack et Jill veulent trouver le mot.
    Jack and Jill want to find the word. (Correct.)

"A"=42090
Jack wants to find a word.
  Jack veut trouver un mot.
    Jack wants to find a word.

"OF"=41472
In point of fact, this is a sentence.
  En effet, c'est une phrase.
    Indeed, it is a sentence. (No good; The key word has been lost!)
What is the weight of all that garbage?
  Quel est le poids de toutes ces ordures?
    Which is the weight of all this refuse? (Close enough.)

"IN"=30077
Jack saw the man in the moon.
  Jack a vu l'homme dans la lune.
    Jack saw the man in the moon. (Correct.)

"IS"=29330
Jack is a boy.
  Jack est un gargon.
    Jack is a gargon. (Nope, not quite!!)
Jack is a man.
  Jack est un homme.
    Jack is a man. (Correct.)

"I"=25765
I saw the harbor lights.
  J'ai vu les lumihres de port.
    I saw the lumihres port. (Wrong!)
I found the word.
  J'ai trouvi le mot.
    I have trouvi the word. (Wrong.)
I want to find the word.
  Je veux trouver le mot.
    I want to find the word.

"YOU"=20377
You want to find the word.
  Vous voulez trouver le mot.
    You want to find the word.

"FOR"=19464
He lived for 47 years.
  Il a vicu pendant 47 annies.
    It has vicu during 47 annies. (Grossly wrong.)
For this purpose, the words are in alphabetical order.
  @ cette fin, les mots sont dans l'ordre alphabitique.
    @ this end, the words are in the order alphabitic. (Trashed.)
But for this purpose, Jack wants to find a word.
  Mais ` cette fin, Jack veut trouver un mot.
    But ` this end, Jack wants to find a word. (Trashed.)
I would do anything for your love.
  Je ferais n'importe quoi pour votre amour.
    I would do anything for your love. (Correct.)

"IT"=19382
I want to put it over there.
  Je veux le mettre 2la-bas.
    I want to put it 2la-bas. (Trashed.)
I want to put it near the moon.
  Je veux le mettre prhs de la lune.
    I want to put it prhs the moon. (Trashed.)
I want to put it under the moon.
  Je veux le mettre sous la lune.
    I want to put it under the moon. (Correct.)

"THAT"=18323
You said that ice is cold.
  Vous avez dit que la glace est froide.
    You said that the ice is cold. (Close enough.)

"BE"=16759
To be or not to be, that is the question.
  Jtre ou ne pas jtre, c'est la question.
    Jtre or not jtre, it is the question. (Trashed.)
I want to be wanted.
  Je veux jtre voulu.
    I want jtre desired.
(I give up on this word.)

"ON"=13941
Jack is on the moon.
  Jack est sur la lune.
    Jack is on the moon. (Correct.)

"WITH"=13023
Jack is going with Jill.
  Jack va avec Jill.
    Jack goes with Jill. (Not good enough.)
Do you want anything with that?
  Voulez-vous quelque chose avec cela?
    Do you want something with that? (Close enough.)

"IF"=12793
If you read this, you will understand.
  Si vous lisez ceci, vous comprendrez.
    If you read this, you will include/understand. (Not good enough.)
If you read this, you will find the word.
  Si vous lisez ceci, vous trouverez le mot.
    If you read this, you will find the word. (Correct.)

"AS"=12335
You looked as if you found the word.
  Vous avez regardi comme si vous avez trouvi le mot.
    You have regardi as if you have trouvi the word. (Trashed.)
You look as if you are with Jill.
  Vous regardez comme si vous jtes avec Jill.
    You look like if you jtes with Jill. (Trashed.)
You write as if you don't speak English.
  Vous icrivez comme si vous ne parlez pas anglais.
    You icrivez as if you do not speak English. (Trashed.)
You look as if you do not speak English.
  Vous regardez comme si vous ne parlez pas anglais.
    You look at as if you do not speak English. (Trashed.)
You sing as if you do not speak English.
  Vous chantez comme si vous ne parlez pas anglais.
    You sing as if you do not speak English. (Correct.)

"THIS"=12050
This man is dead.
  Cet homme est mort.
    This man died. (Close enough.)
(New ditty: This old man, he is dead, he played nick-knack on my head.)

"OR"=11937
The man is dead or alive.
  L'homme est mort ou vivant.
    The man died or alive. (Bletch what a screwed rhyming translation!)
The moon is yellow or orange.
  La lune est jaune ou orange.
    The moon is yellow or orange. (Correct.)

"NOT"=11880
The man is not a woman.
  L'homme n'est pas une femme.
    The man is not a woman. (Correct.)

"ARE"=11230
Jack and Jill are on the Moon.
  Jack et Jill sont sur la lune.
    Jack and Jill are on the moon. (Correct.)

"AT"=10712
Jack found the word at noon.
  Jack a trouvi le mot ` midi. (Trashed already.)
Jack sang at Jill's window.
  Jack a chanti ` la fenjtre de Jill. (Trashed already.)
You will find at least five words.
  Vous trouverez au moins cinq mots.
    You will find at least five words. (Correct.)

"WAS"=10560
Jack was on the moon.
  Jack itait sur la lune.
    Jack itait on the moon. (Trashed.)
The moon was yellow.
  La lune itait jaune.
    The moon itait yellow. (Trashed.)
The moon was rising.
  La lune se levait.
    The moon rose. (The key word was lost.)
The key word was lost.
  Le mot cli a iti ditruit.
    The word cli has iti ditruit. (Trashed.)
Jack was finding the word.
  Jack trouvait le mot.
    Jack found the word. (The key word was lost.)
Jack was singing the first song.
  Jack chantait la premihre chanson.
    Jack sang the premihre song. (The key word was lost.)
Who was that masked man?
  Qui itait cet homme masqui?
    Who itait this man masqui? (Trashed.)
(I give up.)

"WILL"=10401
Jack will find the word.
  Jack trouvera le mot.
    Jack will find the word. (Correct.)

"BY"=9601
"BUT"=9597
"HE"=9318
"FILE"=8972
"FROM"=8949
"HAVE"=8752
"HER"=8323
"ME"=7942
"SHE"=7792
"WHEN"=7183
"WHICH"=7124
"ONE"=6899
"SO"=6861
"ALL"=6788
"THEN"=6738
"MY"=6685
"X"=6163