var bgScrollTid="";

function changeBackground(bg) {
    document.body.style.backgroundImage="url("+bg+")";
    document.body.style.backgroundRepeat="no-repeat";
    document.body.style.backgroundAttachment="fixed";
    document.body.style.backgroundPosition="top center";
}

function bgClickArea() {

    var p=0;
    var al=1000;
    var ww=document.body.clientWidth-al;
    var aw=parseInt(ww/2);
    var bgLeft=document.getElementById("bgclick_left");

    if (aw>0) {
        al=al-aw;
        bgRight.style.left=al+"px";
        bgLeft.style.height=document.body.clientHeight+"px";
        bgLeft.style.display="inline";
        bgRight.style.display="inline";
    } else {
        aw=0;
        bgLeft.style.display="none";
        bgRight.style.display="none";
    }

    p=p+document.body.scrollTop;
    bgLeft.style.top=p+"px";
    bgRight.style.top=p+"px";

    bgLeft.style.width=aw+"px";


    return;
}