<script>
function up()
{   
    var b = document.getElementById("hidd");
    var a =b.value;
    a=parseInt(a);
    if(a>=4)
    {
        a-=4
    }
    else 
    {
        alert("当前已经是首页")    }
    b.value=a;
}
function down()
{
    var e = document.getElementById("hidde").value;
    e=parseInt(e);
    var b = document.getElementById("hidd");
    var a = b.value;
    a=parseInt(a);
    if(e!=0)
    {
        a+=4
    }
    else
    {
        alert("当前已经是尾页");
    }
    b.value=a;
}
</script>