Sitefinity uses navigation controls - RadControls like RadMenu, RadTabStrip, RadTreeView, RadPanelBar. The controls are styled through skin files and Theme stylesheet with css selectors. At runtime you can change the skin of a control or page theme. You might find these articles useful
The built-in skins are shipped with RadControls installation. Sitefinity only contains Telerik.Web.UI dll that you can reference.
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