A link consists of at least one URL and a libelleé. A link without a link makes no sense and may not be understood correctly or through either by a person or by a tool.
Objectives
Prevent possible incomprehension of links.
Avoid links that become invisible when CSS styles or background images are not included.
Improve accessibility of content to readers with disabilities
Implementation
Give each link a text label (between opening and closing tags of the elementa) or, if necessary, via the textual alternative of an img element or object, etc. Do not hide the text label of the element to replace it with a CSS style effect (background image).
Control
On each page containing hyperlinks :
check that there is content in the tag has a text link, even when styles are disabled or only colors are disabled
check that there is a textual alternative in case of an image link or equivalent, e.g. object and embed elements, even when styles are disabled