Michael Kischner gave us a nice example:
"Consider a case in which young Jeremy, not
a stellar student, comes home and
announces: "If I get A's on my next three
French tests, I can get a C in the course!"
 
Jeremy's father (whom Jeremy will remember
as the kind of father for whom
Jeremy could never be good enough),
answers, "That's a big 'if'!"
 
Jeremy's mother (a saint), answers, "A C in
French -- won't that be wonderful!"
 
For the father, the main idea was in the
subordinate clause; for the mother, it was in
the main clause.  Neither structure nor
placement has anything to do with it!
 
Michael Kischner
 
+++++++++++++++++++++++++
 
Michael considers the father's focus and the
mother's, but what he overlooks is Jeremy's
focus. More context would help, but it seems
clear to me that, for Jeremy (not a stellar
student), the more important idea is the
possibility of the C:
 
 "If I get A's on my next three French tests, I
can get a C in the course!"
 
Note that if Jeremy were more realistic, the
focus would probably have shifted to:
 
 "If I want to get a C in the course, I need to get
A's on my next three French tests."
 
Although I disagree with Michael, I'd like to
note that his comment is one of the  more
interesting that I have seen in this thread.  I'm
worried that too much of the discussion has
been by linguists using big terms which may
intimidate those on the list who are more
interested in the problems in the
writing/reading classrooms. I, for one, am
working with students, some of whom use no
subordinate clauses in their writing. In class,
as we analyze passages of their work and
discuss the effects of clauses, one of the
things I point out is that subordinate clauses
push the information in them into the
background, foregrounding the ideas in the
main SVC pattern.  "More important," to me,
means more important to the message of the
writer/speaker. [Note, for example, that I
subordinated "as we discuss."]
       Finally, I am disturbed when I am told that
"wh" clauses "should not" be considered
subordinate. "Should not" according to
whom? Although this listserver is for the
discussion of teaching grammar, perhaps we
need to keep in mind that there are different
theories and different grammars for different
purposes.