CSS Drop Down menus don't appear in IE 7

In my web site at: http://www.mensdiscipleshipnetwork.com

I have pure CSS drop down menus. They seem to work with Internet Explorer 8 and 9, but in IE7 the drop down menus don't appea开发者_StackOverflow中文版r at all. I changed the z-index to 1000 on the div where the navbar resides, however, it still doesn't work. I saw from another similar question someone suggested applying the z-index to the ul tag. This did not work either. Any suggestions?

Thanks in advance.

Use a different solution which does not involve z-index, such as one of the following:

• float-drop menu
• time dropdown menu
• time flyout menu