Firebug integrates with Firefox to put a wealth of development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page...
Firequark is an extension to Firebug. Firequark extracts css selector for a single or multiple html node(s) from a web page. The css selector generated can be given as an input to html screen scrapers like Scrapi to extract information.