var img = new Array;

img[0] = "header_bg1";
img[1] = "header_bg1";
img[2] = "header_bg2";
img[3] = "header_bg3";
img[4] = "header_bg4";
img[5] = "header_bg5";
img[6] = "header_bg6";
img[7] = "header_bg7";

function random_img(){
        var i = myrandom(img.length) - 1;
        document.write("<div id="header" style="background:url("http://www.ladish.jp/user_data/packages/default/img/orijin/"+img[i]+".jpg");
	background-repeat:no-repeat;">");
}
function myrandom(max){
        var v = max * Math.random();
        if(v == 0.0){v = 1;}else{v = Math.ceil(v);}
        return v;
}