Question marks and exclamation points that denote a move as bad or good are ubiquitous in chess literature.
[1] Some publications intended for an international audience, such as the Chess Informant, have a wide range of additional symbols that transcend language barriers.
The nature of a mistake may be more strategic than tactical; in some cases, the move receiving a question mark may be one for which it is difficult to find a refutation.
A move that overlooks a forthcoming brilliant combination from the opponent would rarely receive more than one question mark, for example.
usually indicates that the annotator believes the move to be dubious[2] or questionable but to possibly have merits or be difficult to refute.
the symbol of the lazy annotator who finds a move interesting but cannot be bothered to work out whether it is good or bad.
Annotators are usually somewhat conservative with the use of this symbol; it is not usually awarded to obvious moves that capture material or deliver checkmate.
For example, in what is known as the Game of the Century, there are two moves by 13-year-old Bobby Fischer which annotators typically award a double exclamation point – 11...Na4!!
The majority of chess writers and editors consider symbols more than two characters long unnecessary.
for an exceptionally bad blunder, or unusual combinations of exclamation points and question marks ("!?!
An exceptionally bad blunder which has sometimes been awarded three or more question marks occurred in Deep Fritz–Kramnik 2006, when Kramnik played 34...Qe3, overlooking a mate in one with 35.Qh7#.
The Nunn convention cannot be used to annotate full games because the exact evaluation of a position is generally impractical to compute.
[6] German grandmaster Robert Hübner prefers an even more specific and restrained use of move evaluation symbols: I have attached question marks to the moves which change a winning position into a drawn game, or a drawn position into a losing one, according to my judgment; a move which changes a winning game into a losing one deserves two question marks ...
I have distributed question marks in brackets to moves which are obviously inaccurate and significantly increase the difficulty of the player's task ...
The best move should be mentioned in the analysis in any case; an exclamation mark can only serve to indicate the personal excitement of the commentator.
[8] Many of the symbols now have Unicode encodings, but quite a few still require a special chess font with appropriated characters.