JS脚本运行报错，被调函数的形参总是提示未定义?报错

// JavaScript Document


function setstyle(){
	if (!document.getElementsByTagName ) return false;
	
	var header = document.getElementsByTagName("h1");
	for(var i=0; i<header.length; i++)
	{
		var elem = getNextnode(header[i].nextSibling);
		elem.style.fontWeight = "bold";
		elem.style.color = "#aa339a";
	}
}

function getNextnode(nod){
	if (nod.nodeType ==1)
	{
		return nod;
	}
	else return (getNextnode(nod.nodeSibling) );
	
}

addLoadEvent(setstyle);
	
总是报错nod 未定义
 求解？？