Article within the menu. Where can I get this theme?

Sory 4 my English.. ‘cuz I’m not using English in daily activity.

I’m looking 4 free WordPress theme. When someone click menu to read the article, it doesn’t action to open a new page. But the article is within that menu.

For details please see adwords.google.com. Under navigation “Learn about AdWords”, there are some sub menus “How It Works”, “Reach More Customers”, “Cost and payment”, etc… When someone click on it, the article is still within that menu (it doesn’t open a new page) but it shows at the right side of menu. Another example is on expressionengin.com homepage. Is there any wordpress theme that contain this feature? If there is no such like them, how can I make it? Javascript programming? Can someone guides me? Thx b4.