Something minor:
You should include the IMG code for the +/- button. I typically can't tell something can be expanded/collapsed without it.
There is a problem with that though... the +/- will show the wrong image initially since it's being collapsed by default. (- to expand and + to collapse. LOL)
I've worked around this by adding another "_collapsed" in the IMG code before the $collapseimg variable, and then creating a 3rd GIF called "collapse_whatever_collapsed_collapsed.gif" which is identical to "collapse_whatever.gif".
That way the right image shows!