The following info is for wm5 users...
Along with the two keys assignments requested by the original poster, there's a list of other useful key assignments that can be made. To see the whole list (where I got the following) go here:
http://www.airfagev.com/howtos_details.asp?id=82
1.Using a registry editor navigate to
KEY_LOCAL_MACHINE\Software\Microsoft\Internet Explorer
2. Create a new key called "KeyMaps" (REGISTRY KEY)
3. Under KeyMaps, create 2 new DWORD values:
50 with a value data 1 (makes the 2 key do page up)
56 with a value data 2 (makes the 8 key do page down)
- OR -
to get a cab file (named Pocket IE Page Up/Down) that will do the registry edit for you, go here:
http://surrealnetworks.com/mpx/SDARegEdits.htm