This works great in Notes but everyone hates them on the web as when you twist a twisty the page is reloaded from the server ... soooo slow. In fact so slow in general I've avoided using them on this Notes based website.
But ActiveRenderer from Radio Userland (developed mainly for weblogs) has twisties too (black ones in this case) and guess what they use JavaScript and CSS to work in the browser. So instant twistiness! Now twisties are usable on the web! On the other hand - if the fully expanded page is very large - you will have to wait longer for the initial download but often that is a beter trade-off.
See here for how it all works. Click on one of the little black triangles to expand or collapse an item - you will get the idea pretty quickly. The content describes how they all work.
When I can find the time I must build them into the views on this website. What I could do with more time!