This tool is for Sokoban fans. You can select an XSB-format plain-text Sokoban level and load it into the online SokoPlayer HTML5 (http://sokoban.ws/sokoplayer/SokoPlayer_HTML5_en.php
After installation, whenever you select some text in the browser, you can right click to popup the context menu. You will see a menu item called 'Copy to SokoPlayer HTML5'.
To make use of this context menu item, follow these steps:
(1) select an XSB format level within your browser, for example, at forums or in emails.
(2) right click to popup the context menu.
(3) click "Copy to SokoPlayer HTML5".
(4) then, Firefox will open a new tab and load that level into the online version of SokoPlayer HTML5.
To test this add-on, try the XSB levels on the following web page:http://sokoban.ws/levels/xsb.php?set=alphabet
The add-on icon is created by Borgar (http://borgar.net