The latest developer release of Chrome got new tab management features and smartphone apps screen while Mozilla mulls a new design for Firefox 5.

Last week, Google updated its developer release of Chrome to version 12.0.712.0. A new feature was spotted that lets you select multiple tabs at once by holding the CTRL key to perform common operation on the group, including closing, reloading and moving tabs. A brand new smartphone apps screen is also available on the new tab page.

Meanwhile, Mozilla, which recently released Firefox 4, is toying with some user interface tweaks for Firefox 5, the next major version of the browser. Mockups are available at the areweprettyyet.com website, representing early ideas that may – and probably will – change down the road. One of the design changes reveals a new account manager that supports multiple accounts.

The feature allows you to sign in to Facebook, Gmail and other sites multiple times using two or more user accounts without the need to fire up a new browser instance for each. Site sign-ins are now possible in a revamped pop-up window, with the URL bar showing the account name being used. Firefox 5 is scheduled for release at the end of June.

After more than a year of development, Mozilla finally launched Firefox 4 for public consumption last Tuesday at 6am Pacific time. More than 8.75 million copies of the browser were downloaded its first day, besting both Firefox 3 which in 2008 clocked in eight million downloads in the 24-hour window and Microsoft’s latest Internet Explorer 9 that launched March 14 to grab 2.4 million downloads its first day. Unlike Microsoft’s latest browser, Firefox 4 runs on the ten-year-old Windows XP and supports Linux and Mac OS X. The counter on Mozilla’s Firefox 4 real-time tracking site was nearing the 38 million count at press time.