You need to put the brakes, on, do some research, and get some advice - well I guess you are doing the latter.
Linux, Apple and Opera are missed out or inadequately covered, as has already been pointed out.
Your biggest mistake is that you have missed out IE6, which is still very widely used. It's still the corporaate standard at the company where I have my day job, due to incompatabilities of later versions with key web-based corporate applications. Browser stats are notoriously unreliable, but around 20% usage of IE6 seems to be about the average, and is similar to stats on sites that I manage (away from my day job, I should add).
DO NOT develop for IE, despite it being the most popular browser. It is the most non-standard conforming browser and it only leads to headaches further on trying to ensure it works in the more standard-conforming browsers.
Most in the business (myself included) develop using Firefox (the developer addons are indispensable IMO), validate the pages, and then apply the tweaks and hacks that are required for IE. There is a LOT of resource on the web to assist with tweaking a valid site to work in IE.
All the above assumes coding the site by hand. If using some kind of wysiwyg-type package it's more of a headache because the generated code is so poor in the first place.
HTH
Dave