<style type=textcss>
.ip_input  { width:20px; height:16px;
font:normal 12px 宋體; color:#000000; border:0px; text-align:center; position:relative; top:1px; }
.all_input  { width:112; height:20px;
font:normal 8px 宋體; color:#000000; border:1px solid #000000; text-align:center; }
</style>

<script language=javascript>

function getPos(obj)
{
　　obj.focus();
　　var workRange=document.selection.createRange();
　　obj.select();
　　var allRange=document.selection.createRange();
　　workRange.setEndPoint("StartToStart",allRange);
　　var len=workRange.text.length;
　　workRange.collapse(false);
　　workRange.select();
　　return len;
}

function setCursor(obj,num)
{
　　range=obj.createTextRange();
　　range.collapse(true);
　　range.moveStart('character',num);
　　range.select();
}

function keyDownEvent(obj)
{
    code=event.keyCode;
    if(!((code>=48&&code<=57)||(code>=96&&code<=105)||code==190||code==110||code==13||code==9||code==39||code==8||code==46||code==99||code==37))
        event.returnValue=false;
    if(code==13)
        event.keyCode=9;
    if(code==110||code==190)
        if(obj.value)
            event.keyCode=9;
        else
            event.returnValue=false;
}

function keyUpEvent(obj0,obj1,obj2)
{
    if (obj1.value > 255)
    {
        alert("填寫范圍必須在 0 - 255間");
        obj1.value = obj1.value.substring(0, obj1.value.length - 1);
        return;
    }
    code=event.keyCode

    if(obj1.value.length>=3&&code!=37&&code!=
39&&code!=16&&code!=9&&code!=13)
        obj2.focus();

    if(code == 32)
        obj2.focus();

    if(code == 8 && obj1.value.length == 0)
    {
        obj0.focus();
        setCursor(obj0,obj0.value.length);
    }

    if (code == 37 && (getPos(obj1) == 0))
    {
        obj0.focus();
        setCursor(obj0,obj0.value.length);
    }
    if (code == 39 && (getPos(obj1) == obj1.value.length))
    {
        obj2.focus();
    }
}
function keyUpEventForIp4(obj0,obj)
{
    if (obj.value > 255)
    {
        alert("填寫范圍必須在 0 - 255間");
        obj.value = obj.value.substring(0, obj.value.length - 1);
        return;
    }
    if(code == 8 && obj.value.length == 0)
    {
        obj0.focus();
        setCursor(obj0,obj0.value.length);
    }
    if (code == 37 && (getPos(obj) == 0))
    {
        obj0.focus();
        setCursor(obj0,obj0.value.length);
    }

}
function getipvalue(obj1,obj2,obj3,obj4,obj)
{
  obj.value = obj1.value + "." + obj2.value + "."
+ obj3.value + "." + obj4.value;
    alert(obj.value);
}
</script>

<form>
  <div class=all_input>
    <input name=ip1 class=ip_input maxlength=3
onkeydown=keyDownEvent(this) onkeyup=keyUpEvent(ip1,ip1,ip2)>.<input
    name=ip2 class=ip_input maxlength=3 onkeydown=keyDownEvent(this) onkeyup=keyUpEvent(ip1,ip2,ip3)>.<input
    name=ip3 class=ip_input maxlength=3 onkeydown=keyDownEvent(this) onkeyup=keyUpEvent(ip2,ip3,ip4)>.<input
    name=ip4 class=ip_input maxlength=3 onkeydown=keyDownEvent(this) onkeyup=keyUpEventForIp4(ip3,ip4)>
    <input name = ipvalue TYPE="hidden">

  </div>
  <INPUT TYPE="button" value = "getvalue" onmouseup=getipvalue(ip1,ip2,ip3,ip4,ipvalue)>
</form>