There has been a little race in the background between Web browser developers to have their Browser be the first to pass the ACID3 reference rendering test. Safari was the front runner until today when Opera overtook it and became the first Browser officially to pass the ACID3 test at 100%. Safari is a close 2nd right now at 98% Firefox 3 beta 4 is at 71% right now.
Awesome, it's about time a browser company has looked at meeting the standards. Maybe MicroSoft will follow suit (haha, I wish).
Just as a followup, Mozilla/Firefox have taken an unusual stand to ACID3 (from their previous history with ACID2). They are giving a similar excuse Microsoft did when IE7 did not support ACID2 and are saying that passing ACID3 was never important in their view - http://shaver.off.net/diary/2008/03/27/the-missed-opportunity-of-acid-3/ as fixing bugs was. If you do read this article, note the responses afterwards including one from the person who made the ACID2 and ACID3 tests as well as from others accusing Firefox of sour grapes. To be honest, I thought after Safari and Opera passed ACID3, Firefox would be at the most 2 weeks away from doing so as well (even if it was an internal test build).