I keep wanting to use Javascript, but I keep remembering some users who deliberately disable Javascript on their browsers.
So should I go ahead and use Javascript thus pissing off those extremely few users, or should I opt instead for an entirely no-javascript site?
Both.
Use CSS where you can (for rollovers, dropdown menues, stuff like that), and do the rest with Javascript. Just make sure that the site still works (just looks less nice) with Javascript and Flash and stuff disabled.
http://en.wikipedia.org/wiki/Unobtrusive_JavaScript
Don,
Depending on your needs, you may want to have full, low-level control of your client-side code (JavaScript). However, if you want to get things done and meet your needs, you may want to check out jQuery (http://jquery.com) if you haven't already. There are many tutorials on the jQuery site that can get you started. Also, you can develop your own plugins for it and submit them, or just use other peoples plugins.
Now, in regards to your question, I would have to agree with iago. Try to use CSS wherever you can due to it being much more efficient (aside from horrible support on some IE versions) than JS.
If you're looking how to do menus and drop-downs in CSS then I have a site that is Perfect for you :)
Stu Nicholls CSSplay: http://www.cssplay.co.uk/menus/ (http://www.cssplay.co.uk/menus/)