var code ; //在全局 定义验证码   
     function createCode()   
     {    
       code = "";   
       var codeLength = 5;//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];   
       }   
       if(checkCode)   
       {   
         checkCode.className="code";   
         checkCode.value = code;   
       }   
          
     }   
        
      function yangzheng()   
     {   
       var inputCode = document.getElementById("user_yanzheng").value;  
       if(inputCode.length <=0)   
       {   
           alert("请输入验证码！");   
           window.event.returnValue = false;	
       }   
       else if(inputCode.toUpperCase()!= code.toUpperCase() )   
       {   
          alert("验证码输入错误！");   
          createCode();//刷新验证码   
          window.event.returnValue = false;	
       }   
       else   
       {   
         if(document.getElementById("user_name").value!=""&&document.getElementById("user_pwd").value!=""){
				;		
		}
		else{
		  alert("请检查您的输入，带*的为必填项");
		  window.event.returnValue = false;			
		}
       }   
          
       }