Porting web apps to Mozilla Mac -- guidance needed

Hello, all. We're a traditionally Windows shop, but want to start building
our Web applications (mostly ASP, ASP.NET) to support the Macintosh
platform. I know we're a little late to the game, but better late than
never! We're completely new to this, and needed some help with a few
questions, and your knowledge and expertise is much appreciated,

    - What are some guidelines for our developers to follow to make Mac
users happy? We heard about not using ActiveX and avoiding client-side
VBScript.
    - On many sites, they have a minimum set of requirements to support
(usually browsers), with Netscape 4.7x and IE 4 being as low as they go. How
about the Mac side? What are some minimum requirements for us to support as
far as browsers are concerned, OS, hardware, etc.?
    - What OS and browser do most users have today on the Mac?
    - Is it a good idea to just develop for Mozilla, or make the sites
compatible with Safari as well? Is there a big difference?
    - We're a state-"funded" university (with "funded" being somewhat of a
joke); should we purchase a Mac for in-house testing, or are there tools
that can check compatibility -- like validation tools that can take a page
and say if it will work/look okay on a Mac?
    - What is a good Web site with info about Mac Web development
questions/requirements? We've found some sites on Google, but they're about
general Web development as opposed to focusing on Mac development.

Thank you much for your input.