XF 1.2 Problem while adding a mobile responsive CSS3 menu on the top of the forum

I have added a css menu css links in the <head> portion of the PAGE_CONTAINER template and the css menu items in the <body> portion. For a logged in user it is working fine at smaller resolutions, but for a logged out visitor, when I decrease the width of the browser (i.e. for mobile resolutions) the css menu items are going above the top header logo and also above the below navbar items. For normal PC resolutions, it is fine for a logged out visitor also. Does it have something to do with the persistent nature of the login bar at the top? Please help me to fix this with any change in the code. Any help will be appreciated. Thanking you in advance. The site: http://ngns.pw