var rndmM = 4;
var sec =(new Date()).getSeconds();
var i = Math.floor(Math.random(sec)*rndmM)+1;
var h_obj = document.getElementById("header_2");


switch(i){
case 1: //丘
 break;
case 2: //チェス１
h_obj.style.backgroundImage = "url(../common/images/itp_h_02.jpg)";
 break;
case 3: //チェス２
h_obj.style.backgroundImage = "url(../common/images/itp_h_03.jpg)";
 break;
case 4: //かめ
h_obj.style.backgroundImage = "url(../common/images/itp_h_04.jpg)";
 break;
case 5: //さかな
h_obj.style.backgroundImage = "url(../common/images/itp_h_05.jpg)";
 break;
case 6: //珊瑚
h_obj.style.backgroundImage = "url(../common/images/itp_h_06.jpg)";
 break;
}