If customization of the top navigation needs to be changed, it must change on the parent site as other Sites are inheriting from this site.

On the parent site, select Site Settings from the Site Actions menu.

Then, select Navigation in the Look and Feel category.

At the bottom of the page, there is a Global Navigational link that represents the top bar links. When these are edited, all of the sub Sites' top bar navigation will be affected.

The Current Navigation header is the site's Quick Launch (Left Side Navigation). The Current Navigation does not inherit from parent sites so this will need to be changed on every Site if required.

To add a category, click Add Heading, and to add a link, click Add Link.

Quick Launch items do not have the ability to be hidden by SharePoint's Audience functionality.

To change the Title, Description, and icon of a Site, click on Site Actions, then Site Settings, and make changes in the Look and Feel category.