The original question asked what makes web2.0 essential for website success. There are a number of factors involved that address this question. Perhaps we could ask a follow-up question for clarification about how web2.0 is necessitated in an ever-growing world-wide-web.

Is the site or blog I run accessible?

How accessible a specific website is can be broken down into a number of components.

1. Does the site run on multiple browsers without error?
2. Is the content-structure logical?
3. Can people find the site?

Does the site run on multiple browsers without error?

web2.0 stresses the importance of compliance with standards such as XHTML strict code. Have you ever opened your website in FireFox? How about Safari? How about Google Chrome? If your answer is "No I've never been on a safari" then your site might not be up to scratch for web2.0.

I used to build websites that looked perfect in Internet Explorer, but soon realized the entire template was messed up in other browsers. Using XHTML compliance eliminates or reduces this problem at great length.

Is the content-structure logical?

Part of web2.0 compliance is organization into logical structures of information.

• Does the site have a clear navigational structure? How about a sub-navigation? Your topics should all fall into about 6-12 main-navigation options and an unlimited number of sub-navigation options below each of these.
• Can the content be searched?
• How are links used on the website?

web2.0 calls for the use of permalinks to prevent broken or changed link content. Imagine if each time we used a static link and the web changes at such a drastic pace -- with pages being deleted and modified all the time -- none of the links would work at all.

In terms of web2.0 contextual links are also important. These links are often found at the bottom of the content or on the sidebar. Contextual links provide links to related articles on the same site (e.g. "Related Posts") and are often auto-generated from a database of content.

Can people find the site?

Perhaps one of the most important developments of web2.0 is social networking. In 2002 and earlier it was almost impossible to get a website indexed in search engines and traffic from search results was slim. Now it's possible to receive thousands of visitors to a blog or website through social networks like Facebook.

RSS is also a part of web2.0. RSS allows each website to have its own unique subscriber base or fan club. Individuals can subscribe to "RSS feeds" and read websites on a number of different devices. Therefore web2.0 can also be considered as relevant in making the web more portable. 

Due to such a large number of components being a part of web2.0 CMS (Content Management Systems) such as Joomla, Mambo and WordPress were developed to make it easier to build and maintain content-based sites.

For example take the software called WordPress. This is a free application that allows multiple authors to create articles and blog posts. It supports:

• Submission to social networks
• Generating automatic contextual links
• Pinging related blogs
• Enforcing permanent links
• Installing an automatic search engine for the entire site
• Publishing an automatic RSS feed

In addition to this most CMS software has a number of other features that make use of web2.0 technologies. Therefore CMS is the means through which web2.0 is delivered and made more usable. web2.0 is essential for web success for website that seek to create logical and clear navigation structures... error-free viewing... and social bookmarking as well as RSS subscription.