Hi Kathy,
I asked a similar question about a year ago, so here's my
take on the subject.
A .chm file is a proprietary Microsoft format so only works
under Windows. You can find programs that interpret .chm files on
other operating systems, but then you have to distribute the
interpreter program as well as the help, and I'm not sure how good
the results are.
WebHelp is the way to go for a Linux environment, although
there are a few oddities in the way it displays. Peter Grainge's
site has an excellent section about WebHelp in other browsers.
Here's
the link.
The main difference between .chm and WebHelp output is that
WebHelp is not compiled, so you have to supply the client with ALL
the output files, not just a single file.
Can't help with context sensitive help as I haven't used it,
but I'm sure somebody else can chime in with the necessary
information.
Good luck!
Anne