//this function will get the current/computed style in IE and Moz/FF
function getCurrentStyle(obj, cAttribute)
{
	//if IE or Opera
	if (obj.currentStyle)
	{
		var curVal = eval('obj.currentStyle.'+cAttribute)
	} else
	{
		//if Mozilla/FF
		var curVal = eval('document.defaultView.getComputedStyle(obj, null).'+cAttribute)
	}
	return curVal;
}
var oDiv = document.getElementById('div');
var divHeight = getCurrentStyle(oDiv, 'height');
alert(divHeight);