Response.Write("<script>confirm('确定所选 "+list.Count+" 项数据的删除？');location.replace(location.href)</script>");
            int result = bll_book.DeleteAll(list);
            if (result > 0)
            {
                Response.Write("<script>alert('成功删除 "+list.Count+" 项数据！！');location.replace(location.href)</script>");
                binbook();
            }

Response.Write("<script>[color=#FF0000]return[/color] confirm('确定所选 "+list.Count.ToString()+" 项数据的删除？');location.replace(location.href)</script>");
            int result = bll_book.DeleteAll(list);
            if (result > 0)
            {
                Response.Write("<script>alert('成功删除 "+list.Count.ToString()+" 项数据！！');location.replace(location.href)</script>");
                binbook();
            }

------解决方案--------------------
C# code


Response.Write("<script>return confirm('确定所选 "+list.Count.ToString()+" 项数据的删除？');location.replace(location.href)</script>");
            int result = bll_book.DeleteAll(list);
            if (result > 0)
            {
                Response.Write("<script>alert('成功删除 "+list.Count.ToString()+" 项数据！！');location.replace(location.href)</script>");
                binbook();
            }

------解决方案--------------------

你应该在弹出提示的时候终止程序的运行
return出去。要继续执行，你需要判断

if(Request.QueryString["step"]=="2")
{
  doStep2();
}

if(Request.QueryString["step"]=="3")
{
  doStep3();
}

明白了吗？