We'll start by looking at some universal patterns, which are the broad trends powering the paradigm, and then get into specific web patterns for elements like the use of tagging and folksonomies, Ajax, and so on.

What Web 2.0 is not

As with any trendy idea that can be used to produce a bag of investment money, some quarters are promoting the artifacts of Web 2.0-ishness in place of the stronger underlying ideas. Do not be confused by this. Using rounded boxes and Ajax do not alone make something useful.