Firefox is poised to deliver some new tools for web developers. When Firefox 10 is released in early 2012 it will add HTML and CSS inspectors designed to help web developers inspect and debug their code. Later releases will add more features, like a 3-D page inspector and even a built-in code editor.

Eventually Mozilla believes the built-in tools will replace the popular Firebug extension for most users, though it will likely be some time before that happens. In the meantime, if you’d like to see the new built-in developer panel in action, grab a copy of the Nightly builds, which all have the new tools in various stages of completion.

It’s worth noting from the start that these tools are not intended to replace the popular Firebug extension for those that need Firebug’s power user features. As Mozilla’s Kevin Dangoor wrote when the project was first announced: “we think Firebug is awesome… that’s why we invest so heavily in it already, more so than for any other add-on. We also want to explore new approaches to developer tools.” In other words devoted Firebug fans need not fret, the popular extension isn’t going away. The coming built-in developer tools are designed to supplement, not replace Firebug for the power user.

That said, the new developer tools will provide many of the basic features web developers require and will likely make Firebug unnecessary for many users.

Although they aren’t yet nicely integrated into a single panel like Firebug offers, by the time Firefox 12 hits prime time the browser will offer a web console, an element inspector with HTML and CSS info, Scratchpad for JavaScript development, a CSS style editor and an error console. Firefox’s view source will also add line numbers, closing a seven-year-old feature request.

The newest of these features is the page element inspector, which is now available in the beta channel. The basic layout of Firefox’s element inspector is a little different than what you’ll find in Chrome or Opera.

When you select “inspect element” Firefox will bring up a breadcrumb-style menu bar at the bottom of the page. To see the actual HTML or CSS applied to that element you need to click the corresponding buttons in the toolbar (or use the keyboard shortcuts). It’s an unusual design decision given that inspecting the element generally means seeing the HTML (at least that’s how every other browser does it), and it means there’s an extra click necessary to get to the same information that’s just one click away in WebKit and Opera.

The element inspector also dims out everything but the currently selected element — the visual opposite of what you’ll find in other browser’s inspectors, which color the currently selected element and leave the rest of the page as is. It’s not a deal breaker by any means, but it can be somewhat jarring when you’re used to opposite look.

On the plus side Mozilla has started work that will integrate the very handy Tilt add-on, which we reviewed a while back, into the inspect panel. The integrated Tilt option is only available in the Nightly channel at the moment, though of course you can just install the Tilt add-on if you want to use it today.

Look for the 3D inspector tools to arrive in Firefox 12 if all goes according to plan. Mozilla also plans to add a themeable Code Editor (so you can edit CSS files, or write JavaScript right in the browser).

While Firefox’s new developer tools are improving (and will be much more useful when the element inspector arrives in Firefox 10), there are still plenty of reasons to prefer Firebug or the WebKit tools. For example, if you open Firefox’s HTML inspector, style inspector and web console all at the same time there’s almost no screen space left for the actual page content. Firebug, WebKit and Opera all save considerable screen real estate by consolidating their tools into a single tabbed panel.

For more details on the new Page Inspector coming in Firefox 10, here’s Mozilla’s screencast overview: