通用于ie和firefox的函数 GetCurrentStyle (obj, prop)

function GetCurrentStyle (obj, prop) {
	if (obj.currentStyle) {
		return obj.currentStyle[prop];
	}
	else if (window.getComputedStyle) {
		prop = prop.replace (/([A-Z])/g, "-$1");
		prop = prop.toLowerCase ();
		return window.getComputedStyle (obj, "").getPropertyValue(prop);
	}
	return null;
}