sup,
sub {
	height: 0;
	line-height: 1;
	vertical-align: baseline;
	_vertical-align: bottom;
	position: relative;
	
}

sup {
	bottom: 1ex;
}

sub {
	top: .5ex;
}

http://www.adobe.com/cfusion/communityengine/index.cfm?event=showdetails&postId=5341&productId=1

Keep consistent line spacing with sup and sub

CSS