Usability

A Definition

The ISO says the usability of an interface is a measure of the effectiveness, efficiency and satisfaction with which specified users can achieve specified goals in a particular environment with that interface.

References

Jakob Nielsen's useit.com is the classic site; but you should also look at Google's directory page for usability too.

Usability Recommendations

Here are some usability "recommendations" that are widely known, though still debated:

• Don't ignore non-English speaking visitors. Provide translation.
• Put the search box on the home page
• Don't overdo it with the graphics
• Make sure visually impaired visitors can still use your site
• Make sure the pages download QUICKLY
• Use thumbnails with links to larger images to help speed downloading (also, the thumbnail needn't be a reduced version of the WHOLE image)
• Make the search engine flexible enough to recognize typos
• Provide consistent navigation throughout the site
• Convey your basic mission on your "home page"
• Frames usually suck
• Splash screens usually suck
• Avoid clutter
• Avoid (too much) annoying marquees and animations
• Don't mess with the default link colors
• Jakob Nielsen's Ten Good Deeds in Web Design
• Avoid each of Jakob Nielsen's Top Ten Mistakes of Web Deisgn
• Avoid each of Jakob Nielsen's Top Ten New Mistakes of Web Deisgn
• Don't move pages. URIs should live forever.
• Avoid absolute font sizes
• Make sure your site is still functional for users that don't have browsers that understand style sheets or can play animations or show images.
• Control the consistency of your site with a single external style sheet, rather than using embedded styles.

Want more? The Nielsen Norman Group will sell you a report with 207 usability guidelines for E-commerce sites.

Miscellany

Ideally you should invest some up-front money to see how users use your site before you launch.

Sometimes usability advocates are criticized for being minimalists who hate graphics, new web technology, or anything pretty.