While viewing a web page, I'd like to issue a search command and have everything on the page disappear except the areas of the page that contain the search term.
Most text editors can show only the lines containing a search term. Sometimes I move the page source to a text editor to do that.
Perhaps a Firefox Greasemonkey script? Start by displaying just the sections that contain the text (paragraph, div, whatever) with some kind of control to expand the scope one notch at a time.