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For the chessvariants forum I would like to add a feature to make it possible to include chess diagrams in forum postings, e.g. through a description of the board position between [diag][/diag] tags. The existing feature for uploading images is not satisfactory for this, as a typical diagram measures about 100KB as an image, and fills up the avalable quota very fast. When embedded in the text of the posting it would only add some 100-200 bytes.

The way I imagined doing this was by providing a JavaScript file that would be executed in the browser client after loading a page with forum posts, which would examine the content of all HTML elements with class="post" for the occurrence of these custom tags, and then replace them by the HTML code to display a chess board as a table of piece images according to the description. I already have such a script that assumes the diagrams are indicated by a HTML tag of a certain class, rather than by a BBcode, but it would only require a very small modification to make it act on the latter.

So my actual questions are:

• How can I cause a given <script> tag that would invoke the required script to appear on every page that displays forum postings?
• It it possible to place the .js file with that script on this server, and how would I know what URL to use i order to link to it?
• Would it be possible to place a set of (tiny, say 33x33 pixel) images of chess pieces on the server from which the board would be composed?