The term “Web 2.0” can be reffered to the extention and ubgradation of “Web 1.0.” It was first coined by Darcy DiNucci in the year 1999. In her article "Fragmented Future," she argues “The Web we know now, which loads into a browser window in essentially static screenfulls, is only an embryo of the Web to come. The first glimmerings of Web 2.0 are beginning to appear, and we are just starting to see how that embryo might develop The Web will be understood not as screenfulls of text and graphics but as a transport mechanism, the either through which interactivity happens. It will [...] appear on your computer screen, [...] on your TV set [...] your car dashboard [...] your cell phone [...] hand-held game machines [...] maybe even your microwave oven.”
This term deals mainly with Web design and aesthetics; she argues that the Web is "fragmenting" due to the widespread use of portable Web-ready devices. Her article is targeted at designers, prompting them to code for an ever-increasing variety of hardware. As such, her use of the term hints at - but does not directly relate to - the current uses of the term. Then, the concept was silent for a few years.

In 2004, the term web 2.0 was popularised by O'Reilly Media and MediaLive. They hosted the first Web 2.0 conference. During the opening session, John Batelle and Tim O'Reilly outlined their definition of the "Web as Platform," where software applications are built upon the Web as opposed to upon the desktop. According to their remarks, the unique aspect of this sudden migration is that the customers are building the business for you. O'Reilly et al contrasted “Web 2.0 with Web 1.0.” They associated Web 2.0 with the business models of Netscape and Encyclopedia Britannica online.

Features of “Web 2.0”:

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“Web 2.0” websites help the user to do more than just retrieve the information. They allow the users to run software-applications totally through a browser. They can also build interactive facilities to provide “Network as platform” computing.

“Web 2.0” sites facilitate the users to own and exercise complete control over the data. These sites encourage the users to add value to applications as they use them.

Bart Decrem, a founder and former CEO of Flock, considers “Web 2.0” as the “participatory Web,” and regards the web as the better source of information as Web 1.0.

Besides these, following are some of the additional features of “Web 2.0”:

Rich user experience
User participation
Dynamic content
Metadata
Web standards,
Scalability
Openness
Freedom
Collective intelligence and
Total user participation, can also be viewed as essential attributes of Web 2.0.
Technology Overview:

Web 2.0 combines the capabilities of client- and server-side software, content syndication and the use of network protocols. Standards-based web browsers use plugins and software extensions to manage the content and the user interactions. Web 2.0 sites provide users with information storage, creation, and distribution capabilities that were not possible in "Web 1.0".

Besides these, Web 2.0 may typically include the following features and techniques:

Andrew McAfee  Uses the acronym (SLATES) for explaining these features and techniques:

Search: Finding information through keyword search.
Links: Connects information together into a meaningful information ecosystem using the model of the Web, and provides low-barrier social tools.
Authoring: The ability to create and update content leads to the joint work of many rather than just a few web authors. In wikis, users can extend, undo and redo each other's work. In blogs, posts and the comments of individuals build up over a period of time.
Tags: Categorization of content by users adding one-word descriptions to facilitate searching, without dependence on pre-made categories. This is referred to as "folksonomy."
Extensions: Software that makes the Web an application platform as well as a document server.
Signals: The use of syndication technology such as RSS to notify users of content change
How does it work:

The client-side/web browser technologies typically used in Web 2.0 development are Asynchronous JavaScript and XML (Ajax), Adobe Flash, and JavaScript/Ajax frameworks such as Yahoo! UI Library, Dojo Toolkit, MooTools, and jQuery.

JavaScript is used by Ajax programming to upload and download new data from the web server without reloading a full page. To continue the interaction of a user with the same page, communications such as the data requests send to the server are separated from the data coming back to the page. Otherwise, the user would have to routinely wait till the whole page gets reloaded. This also improves the perform of a page as the information request will be sent faster compared to the previous version of Web 1.0.

The data received by an Ajax will be formatted in XML or JSON. When this data is received through Ajax, the JavaScript program then uses the Document Object Model (DOM) to dynamically update the web page depending on the new data. These sites also allow for a rapid and interactive user experience.

In short, using these tips and techniques, the web designers can make  their web pages to function just like the desktop applications. For example, Google Docs uses a technique to create web-based word processor.

Adobe Flash is another added technology used in Web 2.0 applications. It’s capable of playing even audio and video files. This has led to the emergence of

www.youtube.com

where the video media is smoothly integrates itself with standard HTML. Besides, it has many capabilities which are not possible  in HTML.

Along with Flash and ajax, Javascript/Ajax frameworks have recently became a very popular means of creating a Web 2.0 sites.  Many of them come with customisable widgets to accomplish such common tasks as picking a date from the calender and displaying a data chart etc.

On the server side, Web 2.0 uses most of the same technologies as Web 1.0. Languages such as PHP, Ruby, ColdFusion, Perl, Python, and ASP.

Usage:

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The popularity of the term Web 2.0 sites has led many in academia and business to embrace this technology. In addition, increasing use of Blogs, highly sophesticated sites, social networking technologies also contributed their own share in popularising this technology.

All these factors helped many in academia and business ubdated their data bases with Web 2.0 technology. As a result, every domain have their web site with 2.0 extention. For example:

Library 2.0, Social Work 2.0, Enterprise 2.0, PR 2.0, Classroom 2.0, Publishing 2.0, Medicine 2.0, Telco 2.0, Travel 2.0, Government 2.0, and even Porn 2.0.

Many web based and desktop applications:

Besides all the advantages mentioned, it also prompted for the origin of many web based and desktop applications. Many new internet applications were originated due to Web 2.0 technology. It has seen many new advancements such as RSS and Atom. Most of these are XML formats respectively.

Thus, the Web 2.0 can be reffered as the extention of Web 1.0. Besides, it’s the sophesticated technology in the current internet era.

In order to design and develop the web sites using the Web 2.0 technology, Dot Logic Web Solutions is rendering its valuable services in the areas of designing, development and training the students in this technology respectively.