<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb2312" />
    <title>js驗證碼</title>  
    <style type="text/css">  
        .code   
        {   
            background-image:url(code.jpg);   
            font-family:Arial;   
            font-style:italic;   
            color:Red;   
            border:0;   
            padding:2px 3px;   
            letter-spacing:3px;   
            font-weight:bolder;   
        }   
        .unchanged   
        {   
            border:0;   
        }   
    </style>  
    <script language="javascript" type="text/javascript">  

     var code ; //在全局 定義驗證碼   
     function createCode()   
     {    
       code = "";   
       var codeLength = 4;//驗證碼的長度   
       var checkCode = document.getElementById("checkCode");   
       var selectChar = new Array(0,1,2,3,4,5,6,7,8,9,'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','wW','x','y','z');//所有候選組成驗證碼的字符，當(dāng)然也可以用中文的   

       for(var i=0;i<codeLength;i++)   
       {   

           
       var charIndex = Math.floor(Math.random()*36);   
       code +=selectChar[charIndex];   

          
       }   
//       alert(code);   
       if(checkCode)   
       {   
         checkCode.className="code";   
         checkCode.value = code;   
       }   

     }   

      function validate ()   
     {   
       var inputCode = document.getElementById("input1").value;   
       if(inputCode.length <=0)   
       {   
           alert("請輸入驗證碼！");   
       }   
       else if(inputCode != code )   
       {   
          alert("驗證碼輸入錯誤！");   
          createCode();//刷新驗證碼   
       }   
       else   
       {   
         alert("OK");   
       }   

       }   

    </script>  
</head>  
<body onload="createCode()">  
<form  action="#">  
     <input  type="text"   id="input1" />  
    <input type="text" onclick="createCode()" readonly="readonly" id="checkCode" class="unchanged" style="width: 80px"  /><br />  
    <input id="Button1"  onclick="validate();" type="button" value="確定" />    
</form>  
</body>  
</html>