<style>
div.IPDiv{background:#ffffff;width:120;font-size:9pt;text-align:center;border:2 ridge threedshadow;border-right:inset threedhighlight;border-bottom:inset threedhighlight; 
} 
input.IPInput{width:24;font-size:9pt;text-align:center;border-width:0; 
} 
</style> 
<script language="JScript" for="document" event="onkeydown"> 
if(event.keyCode==13)event.keyCode=9; 
</script> 
<script language="JScript"> 
var IPlikeInputStr=[]; 
for(var i=0;i<4;i++)IPlikeInputStr[i]="<input class="IPInput" name=IPInput type=text size=3 maxlength=3 onkeydown=‘if(event.srcElement.value.length==3||event.keyCode==39)event.keyCode=9‘>"+(i==3?"":"."); 
document.write("<div class="IPDiv">"+IPlikeInputStr.join("")+"</div>"); 
</script>
摘自 : http://www.jb51.net/article/590.htm
原文:http://www.cnblogs.com/18JG23/p/6567415.html