From Fuel Your Creativity:

In the instant design age many of us often stray away from the basics in design. If you had a professor in college who taught you the fundamentals of design these may be engrained into your skull. For the self-taught, you may have a book on your desk with these very principles that you refer to on a daily basis.

http://www.fuelyourcreativity.com/the-lost-principles-of-design/

Drop-down menus are an excellent feature because they help clean up a busy layout. When structured correctly, drop-down menus can be a great navigation tool, while still being an attractive design feature.

http://devsnippets.com/article/slick-drop-down-menu-with-easing-effect-using-jquery-css.html