AJAX, a technique used sparingly

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Content of this article

This article explains what AJAX is, when to use and what contraindications. We also show how to overcome some of the contraindications.

What is AJAX?

AJAX stands for: Asynchronous JavaScript And XML. That is, the combination of JavaScript and XML asynchronously.

It is a technique developed for interactive Web applications, which consists of a set of three existing technologies work together effectively.

These technologies are:

  1. (X)HTML y CSS (Cascading Style Sheets) to give a structure and present the information on the website.
  2. JavaScriptUsed for dynamic interaction with data.
  3. XMLUsed for interaction with the web server. Although it is not necessary to use XML simpre with AJAX applications, as for example, plain text files can also be stored information.

Like DHTML, AJAX is not itself an independent web technology, but a term that encompasses the three aforementioned technologies.

What is Ajax?

Ajax is used to make changes to a web page at the user, without having to reload the whole page again.

For example, on a web page the user requests any information that is offered from the same web page (such as a description of a product) and click on the link on the same page (without loading it again) the requested information appears .

The process of displaying HTML data made entirely consume significant bandwidth, since all HTML should again be loaded to only show the changes. Instead, an AJAX application is much faster and consumes bandwidth.

The JavaScript used in AJAX application is a dynamic, able to make changes to a Web page without re-charge language. AJAX makes sure that only the necessary information is requested and processed, using SOAP or other Web services language loosely based on XML.

Hence a technical level, 3 advantages are obtained: one time charge much lower, saving the user bandwidth and server load much less where the website is hosted.

AJAX problems

Problems with search engine indexing:

AJAX is used by Google, Yahoo, Amazon and a lot more than search engines, portals and content creators, but not general use and massive as some think. Google, for example, which supports webmasters to use AJAX in their programming, uses it himself in GMail, Google Suggest, Google Maps, but not absolutely all your web pages.

The problem with AJAX is that the content displayed within the application using AJAX, not indexed in search engines. This is because spiders (spiders) search engines are not able to interact with the AJAX application and get the command that displays the content is activated.

Hence, it is a bad idea for example, create a list with the names of our products and make an AJAX application by clicking on a product name, product description and photograph is displayed to the right of the list. If we do this, descriptions of products and their images will not be indexed or Google or any other search engine.

Although not all bad news, certain ways of working with AJAX itself that index, for example, playing a show or not show content using positive and negative margins. So just to bear in mind when scheduling if spiders may pass or not can spend.

Accessibility problems:

If we start from the basis that our website should always be accessible to all types of browsers and users and should at least meet the standard A W3C (http://www.w3.org), We find that most scripts that improve appearance and interactivity of a website have accessibility issues. The AJAX also has them.

As we have seen at the beginning of this article, the use of AJAX involves using JavaScript, and some browsers do not support this type of programming. Although as we shall see it is solvable.

But keep in mind that a large part of AJAX applications that we find in the libraries that exist on the Internet have not corrected this problem and therefore are apps that do not meet the W3C standares (at the end of these lines provide links to libraries code and articles dealing with the issue of accessibility and AJAX).

AJAX, to use sparingly

As we have seen in previous section, although AJAX applications provide dynamic, interactive and reduced bandwidth to a website, they also have drawbacks to search engine indexing level and level of accessibility. Therefore, we must consider and neutralize the following:

  1. If we use AJAX on our websites, we must be aware that the content displayed within the AJAX application will not be indexed by search engines. To remedy this detail, we can create this redundant content and make it accessible to the spiders through a sitemap or through links in the footer of the website.
  2. If we use AJAX to make our website interactive, we must keep in mind that will not meet the Level A accessibility, unless we use the code libraries adopted by the W3C or means to surf the web without using JavaScript.

related links

New information on Google indexing AJAX (March 2010): http://code.google.com/intl/es/web/ajaxcrawling/

Examples of Web pages that use AJAX and AJAX code libraries for use by webmasters:

Articles which explains how to get AJAX code that does comply with the level A W3C accessibility:

List common accessibility errors:

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