im not sure but i think i doesnt work in netscape. should work in all the other ones compatible with IE. anyway, what i usually do is, i detect the browser, if it is IE i dynamically generate a button to add the bookmarking script i've said above. if it is netscape, instead of the button, i generate a message "Press ctrl-D to bookmark my page" (ctrl-D is the hotkey in netscape to add to favourites).
luv
Karthik.