@JosDuchIt
Assuming you have SYS:Prefs/URL prefs properly set in the FILE tab, this works:
URLOpen PROTOCOL FILE "ram:mydir/somepage.html"
The advantage of using URLOpen is that it will still work if you switch browsers in the URLOpen prefs.
If you really want to call Odyssey directly try:
APPDIR:Odyssey "
file:///Myfullpath/mypreferredpage.html"Notice that my command has 3 slashes (///) after "file:" instead of two slashes like your command. Also your http protocols in your post have 3 t's instead of just two. Should be http: and not htttp: