Every chess diagram on the Internet should be interactive in the following ways:
One can generate the FEN of the position that is shown on the diagram.
One can generate the PGN of the game fragment of an animated diagram.
One can easily start an interface that allows making moves on the chessboard to study the position by analysis.
One can easily start an interface for playing the position against computer from both sides.
Play against computer should allow the user to make all the moves by oneself and force the computer to move at any moment.
The positions and game lines that are played out in the two points above should satisfy the first points of always being able to generate the FEN and PGN.
The board can be flipped at any moment so that there is always the choice between having White or Black at the bottom.
The Apronus.com chess service implements this vision and is available to anyone for free.
Additionally, you can make static and animated diagrams as images for posting in your blog or website.
Chess authors can participate in this vision by placing links to Apronus.com pages with the chess content encoded in the links.
For example, you can wrap the <a> HTML tag around any image of a chess position
and put a link into href that encodes the position and directs the user to play against computer at Apronus.com.
The interfaces here provide ready-made HTML code to embed in your pages.
Different chessboard dimensions for chess variants