Usually when I code, I make a whole separate other style sheet just for IE itself. Then if someone is viewing in IE, the normal style sheet... PLUS the IE specific one is called.
Helps keep down the clutter in the main style sheet, and doesn't confuse others regarding other css coding for the main browsers (that are good at reading and handling code). And for PNG, I'll use a PNG "fix" via javascript.
"Correctly handle PNG transparency in Win IE 5.5 & 6.
http://homepage.ntlworld.com/bobosola. Updated 18-Jan-2006."