In the chess mentor lesson "Look What I Found" from the course "Introduction to Tactics" (http://www.chess.com/chessmentor/view_lesson.html?id=1519) the mentor disqualifies 1. Ng8 saying:

"This leads to a repetition of moves after 1...Ke8 2.Nf6+ Kf8. Note that 1...Kxg8?? allows the queen to deliver checkmate on either g7 or h8."

this comment is incorrect as after 1...Ke8 White will take the queen on e7 with the same result as the correct solution 1.Nd5.

Why is not only the correct move 1. Ng8 disqualified and score points detracted, but also with a faulty comment misleading players attempting the problem?

Thank you for reporting this error. I have now adjusted the response text for 1. Ng8

Here's another one: http://www.chess.com/chessmentor/view_lesson.html?id=349&c_id=17

After b7 Ka7, b8=R! is just as good as b8=Q! because black is in a zugzwang wherein (s)he must take on b8 and face Kb6 Ka8 Kc7 etc.

And another: http://www.chess.com/chessmentor/view_lesson.html?id=361

The critical position has a white king on c5, a white queen on b8, a black king on g2, and a black pawn on h3. Chess mentor dismisses off Kd4 saying that h2 will draw. However, white's king is in the winning zone for the a-pawn (d1-d4-e4-e5-h5-h1), so white wins easily with Kd4 h2 Ke3 with a mating attack to follow, which I'll allow readers to find as a calculating exercise.

Thanks, I have now fixed the one you reported above, lesson ID 17.

Also corrected lesson ID 361.

Great work! :)

I have another mistake...

http://www.chess.com/chessmentor/view_lesson?id=6266&c_id=343

I don't know if that's the right link.  It's under "The Drawing Zone" part 1.  "The Best Chance".  There's a position almost at the end where the white King is on A3, and the black rook is on F1.  Black makes a King move, but RF1-A1 is mate.  I verified the position on a computer board to ensure I wasn't not seeing something it is mate.

I'm doing the mentor course "Rook & Other Endgames" It claimes to have 142 questions, but there are 11 missing. When I completed all questions; it said I was 93% complete. Is there something I'm missing here?  Also, the explanations tell you to see variation 1 or 2, etc.  How do I do that? Other than that, I love your site. I've completed about 12 mentor courses with no problem.  Thank You rcote63@yahoo.com

Thanks moviemaster, however the object is to play as WHITE in that lesson and find the best moves for that side. Black may not have played the best way to illustrate an instructional point from the White side.

http://www.chess.com/chessmentor/view_lesson?id=1072

Averbach-Ravinsky, Moscow 1950 seems to have a problem.  I think it should be checked with an engine for accuracy.  Other moves seem more logical and easily winning.

I think you're right, I just had a go at it and my first two 'guesses' were incorrect.

g3 looks a better option to me, but mentor tells me    "1.g3 is met by 1...Bg6! when 2.Bb3 Be4+ is really annoying."

After 1...Bg6, White would surely play Bxg6.

Same here, I tried g3 and g4.  It says g4 actually loses material if you try that option. (Which must certainly be incorrect)

g3 is the best move (Houdini).

I searched for the game on chesstempo.com and found that White did in fact play chess mentor's move (29.Bb3) in the position given...

I like to see the staff correcting things in Chess Mentor. Chess Mentor is the definitive feature that made me deciding for a premium membership. When we try to build something as Chess Mentor, errors like these reported here will occur unendingly. The good news is: the connection community-staff is becoming more effective, I would say. Good work, staff. Just remember I sent you some corrections written, literally, by Capablanca himself on moves of one of his own games! I don't know whether they have been already implemented. Never take my posts as negative criticism. I'm in chess.com because I like very much the site and I really prefer it to its competitors. Cooperation is a two lanes way: improve me and I improve you. Chess Mentor improves my understanding in chess. Visibly.

Another correction:

In the lesson "Looking for the classical smothered mate" from the course "essential checkmate patterns", link:

http://www.chess.com/chessmentor/view_lesson?id=1273

There are two instances in the main line where it's explained that the white king cannot escape to f1, since then ...Qf2 would be mate. In fact, the king cannot escape to that square since it's controlled by the a6 bishop, so the moves it makes (in both cases, to h1) are forced.

I also posted another correction in another thread:

http://www.chess.com/forum/view/chess-mentor/deadly-diagonal

Moderators - if this is the thread for corrections, please delete the unnecessary additional one.

A very light improvement:

http://www.chess.com/chessmentor/view_lesson?id=926

Instead of Taimanov-Botvinnik 1953, the correct date seems to be 1952, as it may be seen here:

http://www.chess.com/games/view?id=58202

Nothing serious, but a correct date helps future searches.

Also in this lesson

http://www.chess.com/chessmentor/view_lesson?id=929

Instead of Taimanov-Kuzmin 1976

Taimanov-Kuzmin 1975, as may be seen here:

http://www.chess.com/games/view?id=241568

Still at

http://www.chess.com/chessmentor/view_lesson?id=938

Instead of Portisch-Taimanov, 1959, Leningrad, although the game is one of a match Budapest-Leningrad in 1959, the correct site of the game seems to be Budapest, and not Leningrad. Many other sources cite Budapest. For instance:

http://www.365chess.com/view_game.php?g=2544765

http://www.chessgames.com/perl/chessgame?gid=1138021