In the left box, enter the path to the icon you wish to use, then click Add. Select the icon in the list on the left, and enter the extension/protocol to associate with it on the right, and click Add. (Extensions must include the ".")
The icon path may include the following variables:
%LASKIN% - points to the Link Alert skin directory.
%LASIZE% - replaced with "large" or "small" depending on settings.
%LASIZEPX% - replaced with "32" or "16" as above.
%LAEXT% - replaced with the file extension of the link.
%LAPROTO% - replaced with the protocol of the link.
To use the system default use moz-icon://.%LAEXT%?size=%LASIZEPX% Built in icons are at %LASKIN%/%LASIZE%/*-icon.png where * is the value in the "File" column above.
To remove an extension or protocol, select the one you wish to remove then click Remove. To remove an entire icon, select the icon to remove then click Remove. (This will also remove all associated extensions/protocols)