Labels should be added to all non-text content; the alt attribute is a requirement for both HTML 4 and XHTML W3C standards based documents.

When trying to decide on the text label required for a particular non-text element, I find it helps to think of them as (roughly) falling into one of three categories: functional, decorative (including layout), or providing content.

Functional

For functional images, including navigation bars (and horizontal rules) the text should describe the function or destination. For example, if an image is used as a search button, the alt attribute could be ‘Search’, if an image is used for navigation the alt attribute should describe the destination.…

Working with non-profits, charities, voluntary and public sector organisations and social enterprises for over 20 years. Jim set up one of the worlds first website accessibility web agencies in the mid 1990s.