POW - Plain Old Webserver is a Firefox extension that adds a server to your browser.
Information and a tutorial for POW can be found at this wiki
http://davidkellogg.com/wiki/Main_Page?origin=moz_pow
and at this post
http://forums.mozillazine.org/viewtopic.php?t=447189
The Plain Old Webserver uses Server-side Javascript (SJS) to run a server inside your browser. Use it to distribute files from your browser. It supports Server-side JS, GET, POST, uploads, Cookies, SQLite and AJAX. It has security features to password-protect your site. Users have created a wiki, chat room and search engine using SJS.
Product's homepage
Requirements:
· Mozilla Firefox
What's New in This Release: [ read full changelog ]
· This version fixes an image corruption issue and adds a Windows BAT file for non-default Firefox install locations. This should allow users to run CGI scripts on Windows more easily.