เช็ค ห้ามเว้นค่าว่างก่อนกด Submit พร้อมแสดงผลเป็นกรอบสีแดง + ข้อความขึ้นเตือน รบกวนทีครับ

<form id="registerform" class="mgm_form" action="http://www.imaes.net/register/" method="post" name="cert" onSubmit="JavaScript:return fncSubmit();">

<select class='mgm_register_field required' name='gym' onchange='findselected()' id='gym'>
<option value=''>.. Select Gym ..</option>
mysql_data_seek ($result_country, 0)
while($test=mysql_fetch_assoc($result_country)){
<option value='$show_country[Short_code_gym]'>$show_country[Gym_member_is_NF]</option>}
</select>

<input id="mgm_register_field_first_name" class="mgm_register_field required" name="first_name" type="text" value="" />

<input id="mgm_register_field_last_name" class="mgm_register_field required" name="last_name" type="text" value="" />

<select id="khan" class="mgm_register_field required" name="khan" onchange="khan_sc()">
<option value="">... Select Khan ...</option>
<option value="101">TAMRA 1 KHAN 1 WAI KRU</option>
<option value="102">TAMRA 1 KHAN 2 PUNCHING</option>
<option value="103">TAMRA 1 KHAN 3 KICKING</option>
<option value="104">TAMRA 1 KHAN 4 KNEEING</option>
<option value="105">TAMRA 1 KHAN 5 ELBOWING</option>
<option value="106">TAMRA 1 KHAN 6 BASIC OF SELF</option>
<option value="107">TAMRA 1 KHAN 7 TECHNIQUES</option>
<option value="108">TAMRA 1 KHAN 8 STRATEGIES</option>
<option value="109">TAMRA 1 KHAN 9 THE ARTS OF WAI KRU</option>
<option value="110">TAMRA 1 KHAN 10 KHRU FEUK HAD</option>
<option value="111">TAMRA 1 KHAN 11 PHU CHUAY KHRU</option>
<option value="112">TAMRA 1 KHAN 12 KHRU</option>
<option value="113">TAMRA 1 KHAN 13 PHU CHUAY KHRU YAI</option>
<option value="114">TAMRA 1 KHAN 14 KHRU YAI</option>
<option value="115">TAMRA 1 KHAN 15 KHRU CHIEW CHAN</option>
</select>

<select id="gender" class="mgm_register_field required" name="gender1" onchange="gender_sc()">
<option value="">... Select Type ...</option>
<option value="M">Male</option>
<option value="F">Female</option>
<option value="K">Kru</option>
</select>

<input id="datepicker" name="date" readonly="readonly" type="text" />

<input id="wp-submit" tabindex="100" name="wp-submit" type="submit" value="Confirm" />
</form>

<script>
 function fncSubmit(){                    
         if (document.getElementById("gym").value.length < 1){
             document.getElementById("gym").style.border = "solid 3px red";
             return false;
          }else { document.getElementById("gym").removeAttribute('style');
                     return false;
                    }
         if (document.getElementById("mgm_register_field_first_name").value.length < 1){
             document.getElementById("mgm_register_field_first_name").style.border = "solid 3px red";
             return false;
          }else { document.getElementById("mgm_register_field_first_name").removeAttribute('style');
                     return false;
                      }
          if (document.getElementById("mgm_register_field_last_name").value.length < 1){
              document.getElementById("mgm_register_field_last_name").style.border = "solid 3px red";
              return false;
          }else { document.getElementById("mgm_register_field_last_name").removeAttribute('style');
                     return false;
                   }
          if (document.getElementById("khan").value.length < 1){
              document.getElementById("khan").style.border = "solid 3px red";
              return false;
          }else { document.getElementById("khan").removeAttribute('style');
                     return false;
                     }
         if (document.getElementById("gender").value.length < 1){
             document.getElementById("gender").style.border = "solid 3px red";
             return false;
        }else { document.getElementById("gender").removeAttribute('style');
                   return false;
                   }
        if (document.getElementById("datepicker").value.length < 1){
            document.getElementById("datepicker").style.border = "solid 3px red";
            return false;
        }else { document.getElementById("datepicker").removeAttribute('style');
                   return false;}
 }
</script>