My question regards DHTML drop-down menus.

Do search engines catalog the links in these kind of menu systems?

Are there different ways of constructing DHTML or javascript menus to increase their search engine friendliness?

Does it make a difference if the scripted links are kept as part of external .js file or written internally within the HEAD of the webpage?

I have a large list of internal HTML text links in the page header on one of my sites and a DHTML drop-down menu would really make the navigation much neater, but I'd hate to reduce my ability to have these links catalogued by search engines.

Thanks in advance,