I tried to rename a character style in default.css to "Code inline". I did this because the other styles (the default styles) included spaces in the style name, e.g. "Expanding text" and "Glossary text".
Eventually I discovered by accident that "CodeInline" works, but not "Code inline". I could not find any naming guidelines in the Help, and so thought that this might be useful to post.
http://www.w3schools.com will help you but the short version is no spaces, don't start the name with a number (can use numbers, just not at start) and stick to alpha numeric characters.
Some other characters are OK but if in doubt, avoid. You may find stuff on the web saying not to use underscores but I have not encountered problems with them. Hyphens are OK.
See www.grainge.org for RoboHelp and Authoring tips