Affiliate Marketing Secrets

Damn, it’s really confusing.As we know a layered approach of OS Design has the hardware at level 0,the basic subroutines above it,then the core OS functions, then system programs and so on as we go up the level with the user interface coming at the highest level.And in the Micro-kernel approach,the basic functions of the OS are abstracted as the micro-kernel.
Now PLEASE tell me, other than terminology, is there any difference at all?Can’t we call the first few layers in the layered approach as Micro-kernel too?
My book (Operating System Principles-Galvin Gagne 7th ed) says the two are different and has separate sections for each,but at the same time adds the following confusing lines :
“Mac OS X structures the operating system using a layered technique where one layer consists of the Mach microkernel” (Chapter 2,section 2.7.4)”
Can any of you fine people answer this question? (I am not sure if I am overoptimistic in expecting answers to questions on “niche” subjects like this, but you see, I have got answers to similar questions on computer architecture on Y!A…..)

According to version tracker ( http://www.versiontracker.com/dyn/moreinfo/macosx/10596066 ), firefox 4 beta 1 is supposed to support PPC Mac 10.4, but for me it crashes on startup. Does anyone else have this problem with a PPC mac running OS X 10.4? Has this bug been reported? Is there plans for PPC support for Mac OS x 10.4?
Thanks for the help,
Ben