Hello

To amend try adding the following to the Custom CSS field of your templates parameters...

#container_hornav {

    display: none;

} 

As you only want to effect the frontpage you will need to add the above CSS to a single template style applied to just that page. For details on creating multiple template styles may I suggest the following article... http://joomla51.com/tutorials/item/creating-multiple-template-styles

Ciarán