The first preview version of Firefox 3.1 will be released tomorrow, according to Mozilla.

The web browser developer, which only released Firefox 3.0 last month, froze the Firefox 3.1 code on Monday, and said it on its website earlier this week that it was "still on track for a Friday release".

A number of subtle changes are expected in tomorrow's release, including a tweak to the way Firefox switches between tabs using Ctrl-Tab. The change will mean hitting that combination will switch tabs between the current and last-viewed tabs, rather than automatically moving to the next tab. The feature was originally planned for Firefox 3.0.

Mozilla said Firefox 3.1 would also feature improvements to the browser's location bar.

Firefox 3.0 review