IE8 test: z-index problem is no more

I have updated my z-index tutorial with tests in IE8 beta 1. There was nothing new to write as IE8 correctly passed all tests and rendered test cases according to CSS2.1 spec. The horrible z-index scripting trickery I used to control complicated layouts (like on boylesports.com) will not be required in few years.

I took the opportunity to add some screenshots of reference rendering vs IE6/7 rendering, to make it easier on those just casually reading to see what the errors are (previously you needed to open the pages in IE6/7 to actually see what is wrong).

Additionally, IE8 also supports :after, which I use for float clearing.
As it is, there will be no need for ie8.css hidden under conditional comments. Yipi! :)