Well, it honestly really depends on what the website is for (advertising) and who your audience is.... if you were a music artist, you'd put a music player or background music... etc
On another note, I'd avoid using frames.
Secondly what really are the determining factors between whether a site is considered non-professional or professional?
You can easily see that yourself if you go to a myspace page (loaded with "junk" that doesn't necessarily add any information about the person whose myspace it is) and then compare it with like microsoft.com ... basically speaking, if you have content on your website that doesn't necessarily add to the purpose of the message that you are trying to convey, I'd consider that unprofessional (except for maybe paid advertising... that's a discussion for another day). Professional has hardly anything to do with how simple or complex your website is... if it is easy on the eye (not all bright red or green), a little graphically beautiful (maybe a header, menu, border graphics, etc), and has content that is relevant, you can get a decent website.
All in all, it's not so much about what not to do, but what your website should do/be ...
You want your web site to be easy to read, navigate, and find. It should also be consistent in layout and style, and should definitely load rather quickly even on a modem connection (alhtough, a lot of people have DSL nowadays).