gnome-help-browser only supports the mousewheel on the scrollbar. Everywhere else it does not. See http://www.inria.fr/koala/colas/mouse-wheel-scroll for configuration instructions; the short answer is that you need to have the Pointer section in the /usr/lib/X11/XF86Config look something like the following (works for me on Netscape with a Microsoft Intellimouse w/Intellieye, anyway): Section "Pointer" Protocol "IMPS/2" Device "/dev/mouse" ZAxisMapping 4 5
We are doing active development on a replacement for gnome-help-browser; Nautilus or Mozilla can be used for now, and a fast standalone browser will appear when we move to GNOME 2.