//此段脚本用来实现一个飘动的层
    var xPos = 20;
    var yPos = document.body.clientHeight-100;
//    var yPos=screen.availHeight;
    var step = 1;
    var delay = 30; 
    var height = 0;
    var Hoffset = 0;
    var Woffset = 0;
    var yon = 0;
    var xon = 0;
    var pause = true;
    var interval;
    pdck.style.top = yPos;
    
    function changePos() {
        width = document.body.clientWidth;
        height = document.body.clientHeight;
        Hoffset = pdck.offsetHeight;
        Woffset = pdck.offsetWidth;
        pdck.style.left = xPos + document.body.scrollLeft;
        pdck.style.top = yPos + document.body.scrollTop;
        if (yon) {
        yPos = yPos + step;
        }
        else {
        yPos = yPos - step;
        }
        if (yPos < 0) {
        yon = 1;
        yPos = 0;
        }
        if (yPos >= (height - Hoffset)) {
        yon = 0;
        yPos = (height - Hoffset);
        }
        if (xon) {
        xPos = xPos + step;
        }
        else {
        xPos = xPos - step;
        }
        if (xPos < 0) {
        xon = 1;
        xPos = 0;
        }
        if (xPos >= (width - Woffset)) {
        xon = 0;
        xPos = (width - Woffset);
           }
    }
    
    function start() {
        pdck.visibility = "visible";
        interval = setInterval('changePos()', delay);
        }
        function pause_resume() {
        if(pause) {
        clearInterval(interval);
        pause = false;
        }
        else {
        interval = setInterval('changePos()',delay);
        pause = true;
           }
    }