There's no question that most people have heard of AJAX by now, or have seen some interesting uses of it. When done right, AJAX dramatically improves the user experience, but using AJAX simply for "style points" can be disastrous:


1. DIV popups (with AJAX-powered content) appearing without the user's consent (Snap Shots)
We've all seen it before. When rolling over text or a hyperlink, a bubble pops up with a screenshot of the prospective site, or sometimes, context-related ads appear. Anything that takes control or surprises the user is evil. I would never wish something so vile for even my worst enemies.

2. Automatically loading more content when the user scrolls down (DZone, Live)
An age old idiom of web and interface design in general is not to break existing functionality. When the user hits the 'End' key, we expect to be sent to the end of the page, for example. Pageless pagination, or Endless Pageless styles of loading more data break every convention that makes the web analogous to physical medium. No longer can you remind yourself, "Oh, that cool widget was on page 3". We use page numbers for a reason, and although these pageless methods are technically interesting and flashy, they do no service to the user aside from a monotonous scroll-wheel workout.

More importantly, AJAX content keeps getting loaded onto the same page. Add a couple hundred items (each with related images and/or embedded media), and your inquisitive user might start wondering why their browser isn't responding.

3. Multi-page forms that don't support the browser's "back" button (PBwiki)
Here we are again, altering the way a user expects the page to behave.

4. Browser incompatibility (mostly IE)
One of the more annoying uses of AJAX is when it doesn't work to begin with. When working with AJAX, I'd say that a good 25% of my time was spent correcting code inoperability among browsers. Thanks to libraries like jQuery, that time has been cut down dramatically. Regardless, if these various browsers simply stuck to the standards instead of being web cowboys, web developers would have a noticeably brighter outlook on life.

Contributors: Mike Shade, Oscar Merida, Sandy Smith