For your site’s navigation menu links, do not use images in lieu of formatted text. Words presented in images cannot be indexed by search engines.
Do not use image maps (i.e., images with multiple clickable regions) for navigation. Their content cannot be indexed by any search engine, their links cannot be indexed by some search engines, and they are not accessible to screen readers for the visually impaired and text-only browsers.
Make sure that the text labels of your site’s navigation menu links are large enough to be triggered separately by the tap of a fingertip on a touch screen device.