Seaside's Halos take the web browser's "View Source" transparency paradigm to a new level. Here are some examples taken from the SmallWiki 2 Seaside application (click the images for more detail).

This is SmallWiki 2 with Halos activated via the "Toggle Halos" link on the bottom command-bar. It show 8 components of the application and their hierarchical relationships. In this example the component SW2TreeComponent has its "XHTML source" toggled on using the [R | S] switch.

The "spanner/wrench" icon in a halo displays a web version of the class browser/editor. This is the SW2HeaderWidget's class Smalltalk source code.

The "eye" icon in a halo displays a web version of the object inspector. This is the SW2TreeComponent.