Three milestone releases of Windows 8 leaked to the general public. Milestone 1, Build 7850, was leaked on April 12, 2011. It was the first build where the text of a window was written centered instead of aligned to the left. It was also probably the first appearance of the Metro-style font, and its wallpaper had the text shhh... let's not leak our hard work. However, its detailed build number reveals that the build was created on September 22, 2010. The leaked copy edition was Enterprise edition. The OS still reads as "Windows 7". Milestone 2, Build 7955, was leaked on April 25, 2011. The traditional Blue Screen of Death (BSoD) was replaced by a new Black screen, although this was later scrapped. This build introduced a new ribbon in Windows Explorer. Build 7959, with minor changes but the first 64-bit version, was leaked on May 1, 2011. The "Windows 7" logo was temporarily replaced with text displaying "Microsoft Confidential". On June 17, 2011, build 7989 64-bit edition was leaked. It introduced a new boot screen featuring the same fish as the default Windows 7 Beta wallpaper, which was later scrapped, and the circling dots as featured in the final (although the final version comes with smaller circling dots throbber). It also had the text Welcome below them, although this was also scrapped.

What does BSoD stand for?