I cannot get the main menu to stay highlighted when going to sub menu or when in a sub menu.
Anyone have a css trick to highlight (maintain the highlight)in the main menu when the sub menu is being hovered or clicked.
As we don't have proper sample code of yours.
To achieve this, I suggest you to use JQuery & CSS for better look and feel.
Below is JQuery plugins URL. You can find 7 styles of horizontal menu's.