Interlaced GIF files download in passes; the graphic first displays at a lower resolution, which can be blurry, before the higher-resolution graphic arrives. Noninterlaced GIF Files images appear in chunks, starting from the top, once each chunk is downloaded. Interlaced GIF files download more quickly than the noninterlaced variety. Many Web designers use interlaced GIF images in the hope that visitors will be less tempted to surf elsewhere if they see the entire graphic is on its way.
GIF Files
Understanding usability
If you want to profit from researcher’s discoveries, you’ll find lots to study at useit, uie and usableweb (the sties of Jakob Nielsen, Jared Spool and information architect Keith Instone, respectively). Some tips to get you started:
Bells and whistles.
In most cases, forget multimedia special effects. Visitors to your sites should not have to use the most recent browser of plug-in program. The most popular sites got that way without the latest gizmos. “Amazon.com is designed to work with Netscape 2.0, ” says Tom Weathington, usability specialists for Deloitte & Touche.
Download times.
Aim to have your page appear in no more than eight seconds, the average of the Internet’s 10 most popular sites. “Slow response times often translate directly into a reduced level of trust and always cause a loss of traffic, ” Nielsen notes.
Link color.
Since the Web’s inception, users have been trained that blue underlined text takes them to another page. Any other color or treatment for hyperlinks decreases usability.
Search boxes.
Contrary to what you might expect, including a search box decreases usability. The site doesn’t “know” the concepts and words people will use to search and can’t deal with user errors like misspelled words. It is far better to put effort into choosing labels that match what the users are looking for. Links tagged with one or two words don’t work as well as those with seven to 12 words, says Spool.
Scannable text.
It is more difficult to read something online than in print. Cutting wordiness increased usability 58% in one test by Nielsen, and formatting information with bullets produced 47% improvement.
Scrolling.
Once upon a time, everyone knew that people hated to scroll down a long Web page. Wrong, says Spool. People are more successful at finding what their looking for on a site with a few long pages than one with a larger number of short ones.
Headlines.
Online headlines often are displayed out of context, and it takes time to click through to the next page. So skip the urge to give pages or gif files Web articles cute, mysterious names, advises Nielsen. Begin with a relevant word, as in “Microcontent: how to write headlines, page titles and subject lines.”
Marcia Yudkin is the author of Internet Marketing for Less Than $500/Year and nine other books.