<script Language="JavaScript">
        function evalform(address)
       {  
         var crucial,message;
         crucial=address.indexOf("@");
         if (crucial==-1)
         {
window.alert("Error!");
            return false;
         }else{
             message="OK!";
             return window.confirm(message);
         }
       }
      </script>表单如下:
         <form onSubmit="JavaScript:evalform(this.email.value);" >
         <input name="email" type="text">
          <input name="yes" type="submit" value="确定" >
         <input type="reset" name="ok" value="重置">
          </form>

解决方案 »

  1.   

    1、定义函数时,要用小写的function
    2、if结构不需要Then
    3、if后面的表达式要用括号括起来
    4、onSubmit最好写成这样"JavaScript:evalform(this.email.value);"
      

  2.   

    代码有两个地方错误:
    1:Function 中F不能为大写,应该为:function
    2: if语句错误,if后面应该是括号,不能有then,这是VBS才用then 
    以下是正确代码!
     <script Language="JavaScript">
           <!--
            function evalform(address)
           {  
             var crucial,message;
             crucial=address.indexOf("@");
             if(crucial==-1)
             {  
               window.alert("Error!");
                return false;
              }
              else
               {
                 message="OK!";
                 return window.confirm(message);
               }
           }//-->
          </script>表单如下:
             <form onSubmit="evalform(this.email.value)" >
             <input name="email" type="text">
              <input name="yes" type="submit" value="确定" >
             <input type="reset" name="ok" value="重置">
              </form>
      

  3.   

    <script Language="JavaScript">
           <!--
            function evalform(address)
           {  
             var crucial,message;
             crucial=address.indexOf("@");
             if (crucial==-1) 
             {  window.alert("Error!");
                return false;
              }
              else
               {
                 message="OK!";
                 return window.confirm(message);
               }
           }//-->
          </script>表单如下:
             <form onSubmit="return evalform(this.email.value)" >
             <input name="email" type="text">
              <input name="yes" type="submit" value="确定" >
             <input type="reset" name="ok" value="重置">
              </form>