IE stylesheet object problem

[rollOrDie]

Im trying to create a script that will edit css rules in both FF and IE, but IE just isn't having any of it! I get an error message saying that 'the object doesn't support this property or method'.

 

Here is my code, can anybody help?

 

var styleSheet = document.styleSheets[1];

if (styleSheet.rules)
{
	var pAbout1 = styleSheet.rules[20].style;
	var pAbout2 = styleSheet.rules[22].style;
	var pAbout3 = styleSheet.rules[23].style;
}

else
{
	var pAbout1 = styleSheet.cssRules[20].style;
	var pAbout2 = styleSheet.cssRules[22].style;
	var pAbout3 = styleSheet.cssRules[23].style;
}

pAbout2.setProperty ('display', 'none', '');
pAbout3.setProperty ('display', 'none', '');