Getting Around: Links
A link is the basic unit of navigation, and merits further investigation.
Of primary importance is that a link should describe what the user is going to "get" when they click it. Users feel "lost" more quickly in sites where the links are terse and non-descriptive (or vague and ambiguous). Annotation of links (adding text to further describe a link) is helpful, but is slower to navigate than a site where the user can determine the destination by the link's name alone.
It's also important for the links in a given set to be differentiated - users were stymied by links on a travel site that read: flights and prices, timetables, fares, and best itineraries. A person looking to book a flight was not sure how to proceed.
Image links can attract attention when they "look like" buttons, but this "weak positive correlation" was outweighed by the slow rendering and poor legibility of image links. Moreover, users who got "lost" on a site, or who were trying to find there way back to a page they had seen before, were stymied because the images did not change color to indicate which pages had been viewed.
EN: I expect some of the problems experienced with image links may have been overcome by technology: increased bandwidth speeds mean that images load much faster than before; increased display resolution increases the legibility. An egregious design can still yield slow-loading and illegible graphics, but the boundary between usable and unusable has been significantly moved since the time the study was conducted.
Links that are embedded in text are not as apparent (readily findable) to users than those that are isolated from text.
Links that wrap are confusing to users - they assume that each line is a separate link. Vertical space, bullets, or other cues help users to recognize that a link is wrapped, but not at first glance.
Links that are internal to a page (targeting anchors within a larger document) can be helpful in finding information, but also can cause confusion: when the page shifts, the user's eyes are focused on where the links were, which is generally not the top of the screen (where they load), and the process of navigating back to the top of the page can be clumsy, even if "return to top" links are provided.
Users may not realize that links point to other Web sites, especially if the links provided are in a list that contains both internal and external links. A clear visual indication is needed - and even then, it's unlikely a user will be able to find their way back to your own site.
While there was no evidence of learning during the course of the tests (people encountered the same problems several times, and were slowed down or stopped each time), there was some evidence that more experienced users were more familiar with links and were better able to recognize when a link took them to a new page, to another location on the same page, or to a page on a different Web site.