"Usability" is a complicated subject now that websites and display devices have gotten so complex. However, there are still a few simple rules that always apply.. Creative art sites of course have different rules...
USABILITY PITFALLS

1Too many menus pointing in too many directions are confusing.

The best site organization is a hierarchical menuing system that shows all the important sections of the site right up front and breaks the sections down in a logical way. Too many menus and lots of linked headlines in the body wastes unnecessary time while the user searches all those words for what he or she wants. If there are too many links, most users will start clicking at random on whatever they think might be right item. If they don't find it in a few clicks, they're off to the next site on the list.

 

2 Text in undifferentiated blobs is unappetizing.

Users are scanning the content to find out what they want to know--they don't read every word until they get to something promising. If it's too hard to scan and locate information, they'll try another site. The text needs to be easily readable, with plenty of spaces, and bulleted or highlighted for scanning.



3 Esoteric menu labels or unlabeled menu graphics are not cute to busy people.

On a business or information site, the navigation buttons must be named in an obvious way. They need to be large enough to see, and placed to reduce mouse movement. If a graphic-only link is used, it needs to be completely cross-cultural--like an envelope for email, or a printer icon for a print-friendly page. The meaning of the graphic link should be self-evident without a click or mouseover.



4 Flashing or moving graphics on the screen distract the user from reading your content.

Surveys show that in mny cases, users not only don't click on banner ads, even still ones, they skip right over anything that looks like it might be a banner ad--and they even skip the copy that is next to the thing that looks like a banner. It's very hard to read with something leaping around in the corner of your visual field. In this case, less is more! What works better are low-key ads that look like editorials copy.