Jakob Nielsen's guidelines for links appearance:
- Links should be coloured and underlined, though exceptions can be made in menus
- Underlining is important for users with low vision and essential for colour-blind users, if you use red or green link colours
- Shades of blue provide the strongest signal for links, but other colours work almost as well!
- Use vivid and bright colours for unvisited links and "washed out" colours for visited links
- Colours for unvisited and visited links should be variants or shades of the same colour
- Use small fonts for nothing but non-important links, such as copyright info
- And, hey, don't underline text that's not a link and don't render text in link colours
Nielsen also dislikes visual effects, when the cursor hovers over a link, but I can't see how this could cause any usability problems.
- The article Guidelines for Visualizing Links
- May 10, 2004
See also: Tips and guidelines (95) Links (19)