As covered on the Mozilla Developer Center, Firefox 3.6 Alpha 1 is now available for download. And we’ve been busy since Firefox 3.5.

Web developers will be interested in a number of features that are new in Firefox 3.6 Alpha 1:

The TraceMonkey JavaScript engine has continued to get faster.

We’ve made a huge number of improvements to overall DOM and element layout performance. In some cases we’re much, much faster. We’ll cover details on those in a later post.

The compositor landing has made it possible to fix a large number of interactions between web content, CSS and plugins. We’ll be talking about this in a later post as well.

We now support the -moz-background-size CSS property which lets you set the size of background images.

We now support CSS Gradients.

We now support multiple background images.

We now support the rem unit as a CSS unit.

unit as a CSS unit. image-rendering is supported for images, background images, videos and canvases.

We now send a reorder event to embedded frames and iframes when their document is loaded.

event to embedded frames and iframes when their document is loaded. We’ve removed the getBoxObjectFor() method. It was non-standard and exposed all kinds of non-standard stuff to the web.

method. It was non-standard and exposed all kinds of non-standard stuff to the web. We now send a hashchange event to a page whenever the URI part after the # changes.

event to a page whenever the URI part after the changes. We now have Geolocation address support for user-readable position information.

support for user-readable position information. We now support the complete attribute on document.readystate .

You can keep track of this list and other features for XUL and add-ons developers on the Firefox 3.6 for developers page on developer.mozilla.org

Unlike the year that passed between Firefox 3 and Firefox 3.5, we expect that this 3.6 release will be released in a small number of months. Our main focus for the 3.6 release will be end-user perceived performance, TraceMonkey and DOM performance and new web developer features.

Enjoy and test away!