Some are changes to the CSS, some to the JS.
I wish I could do that to IE6 users, but 10% is still a lot and many of those users don't know better. If someone told my father that "IE6 is bad, you need to upgrade to Firefox" he wouldn't have the slightest idea what it meant. All he knows is that the red fox icon on my T-shirt is the same as I have told him to click when he wants to go on the internet
Anyway, in the 4.1 version I have moved more IE6 specific stuff out to the highslide-ie6.css style sheet. In some years we can forget about those hacks.