Firefox recently released Firefox 3.5 the faster version of Firefox browsers. This time they are really doing faster and released the mockups for Firefox 3.7 and now Firefox 4.0 as well. Previously we had shown you the first snaps of Firefox 3.7 and now here is the mockups of Firefox 4.0 on different versions of Windows 7, Vista.
There are some changes expected in the status bar where the go button turns green when you will start typing the URL over there. You can also see the status green line showing the page load status in a very cool manner. You can see the tabs in Firefox 4.0 which is looking bit similar to the Google Chrome browser.
Source: Firefox Wiki