This is a Mac OS X service.
headerdocServices is a little program which takes the current text selection or file selection and process it with the headerdoc2html script to get the code documentation.
When you're building the code documentation from the text selection, the documentation is then displayed in a web browser. The browser used to display the preview documentation is the one selected in the Internet System Preferences panel.
What's new in this version:
New: support for file selection.