To run the extension in Firefox from this checked out source tree: 0. Quit Firefox. 1. copy tabulator@csail.mit.edu to your firefox 'extension' subdirectiory of your Firefox proile directory (see http://kb.mozillazine.org/Profile_folder) 2. change the line of text in tabulator@csail.mit.edu to the location of ~2007/tab/ext/ on your filesystem. like for exmple: /devel/dig/2007/tab/ext 3. Restart FireFox. That's it. You should not have to do any of the things below. To get future versions, just quite Firefox, svn update, restart Firefox. If it doesn't work: 1. Go to about:config by typing it in Firefox's address bar, then type "accept" in the filter. Change the Accept headers which Firefox will use by editing the string to append: ,application/rdf+xml,text/n3=0.98 This is done by the 2. A good first step in the debug process is to try and clear your XPCOM Component registry is to delete xpti.dat and compreg.dat from your Firefox profile directory.