I find it really iritating that seach engines do not seem to recognize that the terms "website" and "web site" are the same thing. If you search for any phrase with "website" in it and then with "web site" in it you get completely different results. And yet you can't optimize for both because it would look unprofessional to write copy with both forms.

So, what can a person do in this situation?

Should I just optimize for what I think is the most common usage and be happy if I can get the page to rank well for it?

Or would it be legitimate to put something like a small "Relevant keywords:" section at the bottom of the page that would have include alternate phrasing.

Is there another solution?

This is also relevant to the broader issue of optimizing for synomyms or different verb conjugations.