I’m bullish on the HCI concept of link scent.  I first learned about it when a co-worker of mine at Homestead.com when to User Interface Engineering (UIE) conference in San Francisco and reported back on what he learned.

The idea behind link scent is simple.  Users don’t click on the best link on an interface to perform their task.  Instead, they click on the link that looks like the link most likely to perform their task based on a quick, cursory scan of the page.  The links on a given page give off a scent, small hints, that users use to judge if it’s the right link to click.

For a link to have good link scent, it should have lots of cues that indicate what lies beneath that link.  The cues can be the title of the link, the URL in the status bar on hover, the alt text on hover, the content around the link, the size of the link, the location of the link… this is not an exhaustive list, but it’s a useful summary of the cues designers should use to create good link scent.

Additional analysis of link scent is available. Also, check out “The way scent works” on this page from the UIE site.
I know this theory sounds very intuitive (so intuitive that it’s uninteresting), but so many sites get link scent wrong.  Dead wrong.  So we need terminology and analogies like link scent to help designers understand their mistakes and build better sites.