Although it's only been around for three months, don't get too comfortable with Firefox 4.
Today, Mozilla has updated the Firefox 5 beta to release candidate status (download for Windows | Mac | Linux), which includes improves support for "future-Web" technology, speeds up the browser, and makes multiple smaller tweaks to the browser.
Following the path cut by Google with Chrome's rapid-release program, the changes to Firefox 5 are several orders of magnitude smaller than those made in Firefox 4 yet are not insignificant. Most importantly, Firefox 5 release candidate makes multiple under-the-hood tweaks to improve performance. … Read more