Here??™s a similar sequence with an Ajax-driven page:
1. The user??™s browser loads the Web page, along with the associated XML data.
2. The user clicks the link on the page, requesting new data.
3. The Ajax engine intercepts the link and sends the data to the browser.
4. The browser displays the page to the user.
In addition to having fewer steps, it??™s also important to realize that no long-distance fetching is involved; all
the data is already loaded into the Ajax engine, ready for delivery. This makes page updates very fast and
also reduces the server load.
Ajax is not without its limitations, however. Because the implementation depends on JavaScript, site visitors
with JavaScript turned off will not have the same experience. Moreover, some browser functionality, like the
Back button and bookmarking, do not work as might be expected with Ajax-driven pages; you cannot, for
example, use the browser Back button to review previous Ajax data selection, nor can you bookmark them.
Perhaps most importantly, accessibility suffers significantly under standard Ajax implementations; only a
handful of screen readers are equipped to handle partial page updates. Designers need to carefully weigh
Ajax??™s pros against its cons before incorporating the technologies into their sites.
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