Working with CSS - here's some handy CSS packages that enable easy drop-down menus that behave nicely with non-css browsers:

 * http://www.alistapart.com/articles/dropdowns/
 * http://htmldog.com/articles/suckerfish/dropdowns/
 * http://htmldog.com/articles/suckerfish/ {{{<---}}} good place to start

 * http://www.lwis.net/free-css-drop-down-menu/
 * http://purecssmenu.com/

Working with ["Javascript"]:

 * Firebug (the obvious way to start): 
 * Internet Explorer work-arounds (working around the lack of the window.console):
   * http://ryan.ifupdown.com/2008/08/29/stop-firebug-console-log-errors/ avoids the errors by installing a window.console with no-op methods ( http://ryan.ifupdown.com/wp-content/uploads/2008/08/noconsole.js )
   * http://icant.co.uk/sandbox/fauxconsole/ shows you the log messages (more useful if you need to do debugging from within internet explorer)