First time I heard of Web 2.0 or web-2, it was year 2006; but it origin since 2004.
Do you know where and how this name came about?
“Web 2.0″ is a weird phrase. It began as the name of a conference, but the people organizing the conference didn’t really know what they meant by it. Mostly they thought it sounded catchy. However, “Web 2.0″ has since taken on a meaning. There are some interesting new trends on the Web, and it’s the nature of a phrase like that to adhere to them.”
But today people introduce it with technology and bringing certain styles to feature the Web 2.0 design.
What special about Web 2.0 from design perspective? Yes, there are some guides or design styles you need to follow:
1. Simplicity
2. Central layout
3. Fewer columns
4. Separate top section
5. Solid areas of screen real-estate
6. Simple navigation
7. Bold logos
8. Bigger text
9. Bold text introductions
10. Strong colors
11. Rich surfaces
12. Gradients
13. Reflections
14. Cute icons
15. Star flashes
Kindly visit Web 2.0 how to design guide.
If you need more references, try to visit go2web20 which listed hundred of Web 2.0 sites.
Is there going to be Web 3.0? Why don’t you click here to find out. 
