Ajax Girl

DD Tab Menu is a standards compliant, 2 level tab menu. Move your mouse over a tab, and a 2nd level content appears beneath it. The script uses CSS to control all of its appearance, and plain HTML to implement the entire menu tabs and contents.

Highlights of this script are:

• Standards compliant, with menu tabs and sub contents defined using
  plain HTML, making customization a breeze. Five styles to choose from by
  default, or customize the tabs yourself.
• Entire menu and its contents search engine friendly.
• Set which menu tab should be selected by default when the page loads
  (ie: 1st tab, 2nd tab etc). If the tab contains a sub content, that
  content is shown as well. Or, have the script automatically
  select a tab when the page loads based on a match between the current
  page’s URL and one of the menu tabs’. If there is a match, that tab is
  selected.

Note that the “auto select tab” feature mentioned above is rudimentary
and isn’t meant to replace directly selecting or using server side
scripting to identify which tab corresponds to the current page. It
won’t account for all possibilities where two URLs are the same. Use it
as a convenience and fallback plan!

Source: Ajaxian
Original Article: http://ajaxian.com/archives/dd-tab-menus