if(document.images){
	//2_0
	var sn_2_1_over=new Image(); sn_2_1_over.src="../img/sn_2_1_over.gif";
	var sn_2_1_off=new Image(); sn_2_1_off.src="../img/sn_2_1_off.gif";
	var sn_2_2_over=new Image(); sn_2_2_over.src="../img/sn_2_2_over.gif";
	var sn_2_2_off=new Image(); sn_2_2_off.src="../img/sn_2_2_off.gif";
	var sn_2_3_over=new Image(); sn_2_3_over.src="../img/sn_2_3_over.gif";
	var sn_2_3_off=new Image(); sn_2_3_off.src="../img/sn_2_3_off.gif";
	var sn_2_4_over=new Image(); sn_2_4_over.src="../img/sn_2_4_over.gif";
	var sn_2_4_off=new Image(); sn_2_4_off.src="../img/sn_2_4_off.gif";
	var sn_2_5_over=new Image(); sn_2_5_over.src="../img/sn_2_5_over.gif";
	var sn_2_5_off=new Image(); sn_2_5_off.src="../img/sn_2_5_off.gif";
	var sn_2_6_over=new Image(); sn_2_6_over.src="../img/sn_2_6_over.gif";
	var sn_2_6_off=new Image(); sn_2_6_off.src="../img/sn_2_6_off.gif";
	var sn_2_7_over=new Image(); sn_2_7_over.src="../img/sn_2_7_over.gif";
	var sn_2_7_off=new Image(); sn_2_7_off.src="../img/sn_2_7_off.gif";
}