Mozilla has quietly released the first beta candidate of Firefox 4 that improved JavaScript engine called JagerMonkey and support Google’s WebM open-sourced video format. The browser will set to launch on November 2010.

The browser prototype sports a redesigned user interface look like Chrome and Opera with tabs up top and sans menu, the browser prototype offers users the options of turning the menu bar back and moving the tabs back down.

Conceivablytech has tested Javascript performance on the beta version, it’s still significantly lagging behind other browsers. Google currently controls its rivals and leads. Firefox may not be able to catch up with the competition for some time.

Download Firefox 4.0 Beta here

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