<pre name="code"><!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>  
       <title>无标题页</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 定义验证码  
        function createCode()  
        {   
          code = "";  
          var codeLength = 6;//验证码的长度  
          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','W','X','Y','Z');// 所有候选组成验证码的字符，当然也可以用中文的  
             
          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("请输入验证码！");  
          }  
          else if(inputCode != code )  
          {  
             alert("验证码输入错误！");  
             createCode();//刷新验证码  
          }  
          else  
          {  
            alert("^-^ OK");  
          }  
            
          }  
            
       </script>  
   </head>  
   <body onload="createCode()">  
   <form  action="#">  
        <input  type="text"   />  
       <input type="text" readonly="readonly"  /><br />  
       <input  type="button" value="确定" />   
   </form>  
   </body>  
   </html></pre>