Ajax is often mistaken for a programming language, when in reality it is more of a standard or technique used to create better, more interactive web applications. It is used to create more responsive web pages by loading certain areas of a page, instead of an entire page. In this tutorial, and the ones that follow, we will learn to work with it to build dynamic web sites.
Believe it or not, even Ajax has some disadvantages to it. Here are some things to consider when deciding whether or not to use it:
-Security
Ajax has been around for a few years now, but it is really still an infant in terms of technology. And like all new (and old) technologies, it is vulnerable to exploits. Of course if this were to stop you, you may as well give up on the web altogether.
-Accessibility
As we've seen before with new technologies, Ajax can sometimes be lacking when it comes to meeting certain accessibility standards.
-Search Engine Optimization
It seems these days that the Internet is only about two things, one of which I can't mention here in this article. The other of course is SEO. Since Ajax loads content after the page loads sometimes, there aren't always good ways to optimize your site so that spiders can crawl it. That isn't to say you can't, but just be aware of the issues and educate yourself.
-Weirdness
Ajax is an evolving technique and as such certain behaviors can occur that you may not expect. It can also be argued that users who are used to traditional web pages might find a page that acts more like an application more difficult to comprehend.
-Timeliness
Even though Ajax should typically speed up your web page, it ultimately is dependent upon the same hardware as other web technologies and thus is subject to the same problems as normal web pages. If a server is experiencing difficulties, it won't matter what you are programming your site with.
Conclusion
Well that is all the time we have for this article. In our next episode we will begin learning the basics of Ajax and how to work with the XMLHttp Request Object. In the meantime you may wish to brush up on your HTML and JavaScript.
AJAX & Prototype 
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