The @blurb directive overrides the text displayed in an index rectangle when hovering over any rectangular link to that page. It also overrides the text in the <TITLE> HEAD element in the HTML head section, and the META description element there as well.

So for example this page's source file has at the bottom:

@blurb @blurb documentation

Blurbs should not contain the " < > ` or asterisk characters and are limited in length to 50 characters.