var img = new Array(); 
img[0] = new Image(); img[0].src = "../images/illust.gif"; 

var xiti = 0;
var yiti = 10;
function bgGo() {
    if(!document.getElementById) return;
    var bcgr = document.getElementById("header");
    bcgr.style.backgroundPosition = 
        xiti + "px " + yiti + "px";
    xiti += -3; if(xiti > 1004) xiti = 0;
    yiti += 0; if(yiti > 1004) yiti = 0;
    setTimeout("bgGo();", 100);
}