Firefox 4 on Mac OS X relies on OpenGL to accelerate some aspects of page construction and rendering. Mac users must have Mac OS X 10.6.3 or later to support all Firefox 4's acceleration.

Some graphics cards and chipsets used in older Macs, including the ATI Radeon X1000 and older, Nvidia GeForce FX and older, and Intel GMA 950 and older, don't support OpenGL and so won't be able to use the technology. Among the Macs with unsupported graphics are the Mac Mini from mid-2007 (which uses the Intel GMA 950).

Mozilla has ended the Firefox 4 beta cycle, and plans to ship the first "release candidate," or RC build, of the browser to the public shortly, possibly this week.

"Unless serious issues are found during in-house testing or its cycle of beta testing, this will be what we ship to users," Mozilla stated on its Web site. "Historically, we have not shipped the first release candidate."

A final version of Firefox 4 should appear this month.