Mozilla hopes to release its fourth beta of Firefox 4 on Monday, adding hardware-accelerated graphics for some Windows users but leaving it turned off by default.

Also coming is a major user interface change called tab sets, formerly known as tab candy.

Hardware acceleration, coming to all the major browsers in various forms, is designed to shift some tasks from a computer's main processor to its graphics processor. One way Firefox is tackling the technology is by using Windows' Direct2D interface, which can speed up the display of text and graphics on newer versions of Windows.

Mozilla planners had hoped to enable Direct2D in the fourth beta, but decided caution was appropriate. "b4 won't have D2D on by default after all; just not quite ready to send it to that many users. soon!" tweeted Mike Shaver, Mozilla's vice president of engineering.