DevTools
O Opera agora usa o Blink / Chromium, por isso tem DevTools do Chromium .
The Chrome Developer Tools (DevTools for short), are a set of web authoring and debugging tools built into Google Chrome [or your Chromium based browser]. The DevTools provide web developers deep access into the internals of the browser and their web application. Use the DevTools to efficiently track down layout issues, set JavaScript breakpoints, and get insights for code optimization.
Firebug Lite
Se você estiver familiarizado com o Firefox e o Firebug, talvez possa tentar o Firebug Lite .
- Compatible with all major browsers: IE6+, Firefox, Opera, Safari and Chrome
- Same look and feel as Firebug
- Inspect HTML and modify style in real-time
- Powerful console logging functions
- Rich representation of DOM elements Extend Firebug Lite and add features to make it even more powerful