Firebug Lite is a bookmarklet port of the Firebug extension. It allows parts of the Firebug functionality to be used on browsers other than Firefox.
Firebug Lite is a JavaScript bookmarklet allowing to debug web pages. It's UI is based on the one of (older versions of) Firebug.
It allows you to inspect the HTML and CSS of a website, provides information about the DOM and offers a console with a command line, where you can execute JavaScript within the context of the web site.
Other features like JavaScript debugging, analyzing network traffic and managing cookies are not supported.
While Firebug Lite is generally available as cross-browser script and bookmarklet, there's also a Google Chrome extension available.
Development
Firebug Lite is currently not actively developed anymore due to a lack of resources. The Firebug Working Group is searching for somebody picking up the development and made its source code available on GitHub.