Based on original Auto-Nav block from Concrete5 Core.
UPDATE (v 0.3):
Now new CSS and support for IE!
Simply install Amiant CSS3 Menu and add it to your page.
Block uses only CSS3 (NO IMAGES).
Package also installs custom attribute for pages, called "Do not display subpages in Navigation".
You need this attribute to disable drop-down submenus for your pages.
For example - in navigation menu you may need "Home", "Blog", "About Us" ..... items.
If you do not add "Do not display subpages in Navigation" attribute to "Blog" page - all of your blog posts will be displayed in drop-down submenu when mouse hover on "Blog" menu item (if you are select to display "All Subpages" in settings of the block).