IE跟FF中获取兄弟节点

function getNextNode(target){
	var rel=target;
	do{
	  rel=rel.nextSibling;
	}while(rel.nodeType!=1)
	return rel
}

firefox 解释：
previousSibling:The node immediately preceding the given one in the tree, or null if there is no sibling node.
nextSibling ：The node immediately following the given one in the tree, or null if there is no sibling node

ie解释：
previousSibling：Retrieves a reference to the previous child of the parent for the object. 获取对此对象的上一个兄弟对象的引用。
nextSibling ：Retrieves a reference to the next child of the parent for the object.获取对此对象的下一个兄弟对象的引用。