The widgets are written in lisp, using the cl-who meta-language. The framework supports "delimited continuations" for control flow. It is a full-stack framework, since it comes with built-in database and persistence systems.
Programming in weblocks is very similar to other Continuation-passing style frameworks like Seaside. All html and http level details are abstracted, especially with regards to Ajax and form parameters (although access to these is easily available).
Weblocks has an active development and user community. The other major Lisp web-framework is UnCommon Web with extensions such as Lisp on Lines that are built atop it.