With the debut of Firefox 3.0 taking place later today, Mozilla has already begun work on version 3.1, which is slated to arrive in early July.

Mozilla's add-on team has been hard at work getting a new version of the add-on web site ready in time for the release. The new site includes a theme browser that displays thumbnails and a new advanced search system, as well as numerous improvements for developers.

Planning is already in progress for Firefox 3.1, which is codenamed Shiretoko. Although still in the early stages of planning, the schedule indicates that alpha releases could be available as early as July. Prominent user interface features planned for the 3.1 release include tab previews and tag auto-completion. Developers also plan to add several new features to Firefox's Gecko rendering engine such as the HTML 5 video element and CSS text shadows.