DOMScope!

Firebug integrates with Firefox to put a wealth of web development tools at your fingertips while you browse. You can edit, debug, and monitor CSS, HTML, and JavaScript live in any web page.

The Google Chrome Developer Tools provide an integrated environment for debugging, optimizing, and understanding a web application, or website, running in Google Chrome. The developer tools are developed partly through the WebKit open source project, where the tools are called Web Inspector.

Examine, edit, and debug HTML, CSS, and JavaScript on the desktop and on mobile.

Opera Dragonfly is a feature of Opera web browser: it is a full-featured development and debugging tool integrated into Opera.

Browsersync makes your browser testing workflow faster by synchronising URLs, interactions and code changes across multiple devices. It’s wicked-fast and totally free.

Whether you want it or not, your site is going mobile - every day. Use Ghostlab to make sure all your users get the same neat experience - whatever operating system, browser or smart phone they are using.

Adobe Edge Inspect is for web designers and developers who are targeting mobile browsers. After installing Edge Inspect on your computer, you’ll be able to pair your devices, have them browse in sync with your computer, and perform remote inspection and debugging so you can see HTML/CSS/JavaScript changes instantly on your device.

SplineTech JavaScript Debugger is the fastest independent standalone JavaScript Debugger that enables you to debug JavaScript for IE completely independently of any add-ons, plug-ins, Java or any other third-party proprietary tools. Native JavaScript, JScript and VBScript debugging languages are fully supported for complex JavaScript, JQuery, HTA, MS Dynamics CRM, Ext-JS and AJAX debugging scenarios.

Code Cola is a chrome extension to editor online pages' style visibility. It helps visual designer, interactive designer, web site operator and other peoples modify the online pages quickly and easily.

Muir is a mobile browser testing app without all the strings of cloud based suites. Simply download the desktop app, install the client on your mobile devices, and get to work.- Browse to any web page in Chrome or Firefox. Your mobile devices will follow suit instantly.- Test responsive designs as you develop. See how each device renders your site.- Connect as many devices as you want via Wi-Fi, and have them all sync to your browser.