Works on SeaMonkey Rated 4 out of 5 stars
Highligher 0.6.5 works on SeaMonkey 2.8 after I edited the install.rdf file in the XPI archive to change maxVersion from 2.1a to 2.8, then re-zipped the files into a new archive and changed its extension from .zip to .xpi. The Highlighter widget appears at the extreme right of the Formatting Toolbar, and one must have a screen width of at least 920 pixels to be able to access it. It would be nice if there were an option to move it to the Mail Toolbar, which has fewer items and would allow the window to be as small as 640x480 (standard VGA). In the alternative, the highlighter function could be added to the Format menu.