function FloatDiv(id) {
    this.ID = id;
    this.ObjMove = document.getElementById(id);
    this.LastScrollY = 0; // 已经移动
    FloatDiv.prototype.Move = function (obj) {
        var scrollTop;
        if (document.documentElement && document.documentElement.scrollTop)
            scrollTop = document.documentElement.scrollTop;
        else if (document.body)
            scrollTop = document.body.scrollTop;
        var percent; // 本次移动像素
        percent = (scrollTop - obj.LastScrollY) * 0.1; // 每次移动10%
        if (percent > 0) percent = Math.ceil(percent); // 截掉小数，数字会变大
        else percent = Math.floor(percent); // 截掉小数，数字会变小
        obj.ObjMove.style.top = parseInt(obj.ObjMove.style.top) + percent + 'px';
        obj.LastScrollY = obj.LastScrollY + percent;
    };
    FloatDiv.prototype.Init = function (obj) {
        if (!obj.ObjMove) {
            alert('对象不存在');
            return;
        }
        window.setInterval(this.BindInterval(this.Move, obj), 10);
    };
    // 绑定参数，window.setInterval，不能指定参数，需要绑定
    FloatDiv.prototype.BindInterval = function (funcName) {
        var args = [];
        for (var i = 1; i < arguments.length; i++) {
            args.push(arguments[i]);
        }
        return function () { funcName.apply(this, args); }
    };
}