This is a design question not a development question so I have moved it from the developer forum to the design forum.
Your question is not very clear but I interpret it to mean you want to show something additional to the menu link for a given menu item. You cannot just add markup into the page name to do this.
If your design is using FlexMenu for the menu, it is capable of rendering also a page description (which can be markup), and there is a database field for MenuDescription for each page. By default this MenuDescription is not shown in PageSettings.aspx because none of the skins we ship with mojoPortal were designed to include the menu description and rendering it in a design that does not expect it just will mess up the menu. However you can make this field appear in pagesettings.aspx by adding this in the theme.skin file of your skin:
If you are not talking about adding extra content per menu item and you just want to put something below the menu, then just add the larkup below the menu in layout.master.
Hope that helps,