See Netscape and Mozilla

When given the URL about:mozilla, the various versions of the Netscape browser would display a message, in white text on a lurid red background, in the browser window. Versions 1 to 4 displayed the following prophecy:

And the beast shall come forth surrounded by a roiling cloud of vengeance.
The house of the unbelievers shall be razed and they shall be scorched to the earth. Their tags shall blink until the end of days.
from The Book of Mozilla, 12:10

"Their tags shall blink" refers to the controversial <blink> HTML tag introduced in an earlier Netscape version. This proprietary HTML extension, which made text blink on and off, was widely derided as annoying, distracting, and ugly. Soon after its introduction, the blink tag joined hideously garish backgrounds and animated GIFs as metonymy for badly designed web pages. The numbers 12:10 refer to the release date of Netscape 1.0, December 10, 1994.

Later Netscape browser versions (as well as the Mozilla browser itself), which were actually based on the Mozilla code, displayed the following:

And the beast shall be made legion. Its numbers shall be increased a thousand thousand fold. The din of a million keyboards like unto a great storm shall cover the earth, and the followers of Mammon shall tremble.
from The Book of Mozilla, 3:31
(Red Letter Edition)

This text probably referred to Netscape's hope that, by opening the Mozilla source, they could attract a "legion" of developers who would help improve the software. Some suggested that "Mammon" referred obliquely to Microsoft, which seemed plausible given that Microsoft's Internet Explorer was Mozilla's chief competition. The numbers 3:31 refer to March 31 1998, the date which Netscape 5.0 was made open source.

The next installment (7:15) is said to be written by Neil Deakin, to mark the establishment of the Mozilla Foundation, which cuts Mozilla loose from its parent company Netscape/AOL. Moreover it hints at the separation of the browser (Firebird) and the mail-client (Thunderbird). This is a reference to the name "Phoenix," which was what Mozilla Firebird was called before the name was changed to avoid copyright difficulty.

And so at last the beast fell and the unbelievers rejoiced. But all was not lost, for from the ash rose a great bird. The bird gazed down upon the unbelievers and cast fire and thunder upon them. For the beast had been reborn with its strength renewed, and the followers of Mammon cowered in horror.
from The Book of Mozilla, 7:15
(Red Letter Edition)