"WEB 2.0" is how you skin your web page buttons Trend, nothing to do with the web itself. It's a simple graphical effect to make image-based objects apear as if they're made of plastic, glass, or some orther polished glossy material.
That's about all the mistery surrounding "WEB 2.0" - A fancy expression.:D
It's an imaginary provoking notion that will lead the subject to pressume that it's something concreete; something new; something cool and advanced he never heard about, making him feel miserable for being such a damn uninformed laggard for something that in reality have never existed.
So: WEB 2.0 is propaganda, - it simply doesn't exist!
A Web 2.0 website typically features a number of the following techniques:
* AJAX and other Rich Internet Application techniques
* Semantically valid XHTML markup and/or the use of Microformats
* Syndication and aggregation of data in RSS/Atom
* Clean and meaningful URLs
* Extensive use of folksonomies (in the form of tags or tagclouds, for example)
* Weblog publishing
* REST or XML Webservice APIs