I'm using the default theme design. Sub-menu of Main Menu are not displaying properly. The background of the sub-menu are not showing. Please see the problem here http://i.imgur.com/cc1Y7Dk.jpg The website I am building is not yet accessible from the Internet. If you try to add a sub-menu to the Main Menu in the demo of the Seven template, you will notice the problem.
I tried to check the document at http://demos.doublemthemes.com/seven/documentation but there is no section relating the menu.
I think this is a bug with theme. Please help fix it.