Is ALT Text for Spacer and Filler Images Required?
Often page authoring tools will insert spacer and decorative images. These images require an ALT attribute, since in its absence screen readers still indicate the presence of the image. Speaking browsers can be ‘instructed’ to ignore these images by using a “null alt text” (alt=””). Browsers will not display a tool tip for a null ALT. The following guideline, which Bobby is based on, specifically mentions spacers (see 1.1): http://www.w3.org/TR/1999/WAI-WebCONTENT-19990505/#gl-provide-equivalents.
