Definitions for "D-Link"
A D-Link is a separate link to an html file that contains a text description of an image/chart/diagram or graph. The D-link is usually signified by a hyperlinked capital [D] in brackets directly next to an image.
a hyperlinked letter d (for description) to the right of an image, as shown here
a link that takes the form of a capital D near an image. It provides a longer description of the image or its purpose than is feasible using an alt tag.