Bookmarklets (aka Favelets) are little snippets of javascript that act on whatever webpage your browser is currently focused on. The first ones Felix had seen did things like post urls to other sites (such as the "Post to del.icio.us" bookmarklet he has copied below); but in fact there are more useful private ones that do things like make named anchors in a page explicit in the rendering of the document.
Several useful bookmarklets are collected at Jesse Ruderman's Bookmarklets Site. Felix found that site when he was searching for a plug-in to render named anchors on a webpage.
He soon discovered that Jesse's code was close but not quite what he
wanted, because Jesse's version only handles anchors that use
the name attribute to name its anchors, but some pages
use the id attribute for that purpose.
With Dave Herman's help, Felix developed the following generalization of Jesse's code: named anchors. Feel free to click it to see the effect, and to drag it to your own bookmarks bar.