Registration form validation using javascript

<script>
    function Submit(){
    var emailRegex = /^[A-Za-z0-9._]*\@[A-Za-z]*\.[A-Za-z]{2,5}$/;
    var fname = document.form.Name.value,
        lname = document.form.LastName.value,
        femail = document.form.Email.value,
        freemail = document.form.enterEmail.value,
        fpassword = document.form.Password.value,
        fmonth = document.form.birthday_month.value,
        fday = document.form.birthday_day.value,
        fyear = document.form.birthday_year.value;
       
    if( fname == "" )
   {
     document.form.Name.focus() ;
     document.getElementById("errorBox").innerHTML = "enter the first name";
     return false;
   }
    if( lname == "" )
   {
     document.form.LastName.focus() ;
      document.getElementById("errorBox").innerHTML = "enter the last name";
     return false;
   }
  
   if (femail == "" )
    {
        document.form.Email.focus();
        document.getElementById("errorBox").innerHTML = "enter the email";
        return false;
     }else if(!emailRegex.test(femail)){
        document.form.Email.focus();
        document.getElementById("errorBox").innerHTML = "enter the valid email";
        return false;
     }
   
      if (freemail == "" )
    {
        document.form.enterEmail.focus();
        document.getElementById("errorBox").innerHTML = "Re-enter the email";
        return false;
     }else if(!emailRegex.test(freemail)){
        document.form.enterEmail.focus();
        document.getElementById("errorBox").innerHTML = "Re-enter the valid email";
        return false;
     }
   
     if(freemail !=  femail){
         document.form.enterEmail.focus();
         document.getElementById("errorBox").innerHTML = "emails are not matching, re-enter again";
         return false;
         }
   
   
    if(fpassword == "")
     {
         document.form.Password.focus();
         document.getElementById("errorBox").innerHTML = "enter the password";
         return false;
     }
   
         if (fmonth == "") {
        document.form.birthday_month.focus();
        document.getElementById("errorBox").innerHTML = "select the birthday month";
        return false;
     }
     if (fday == "") {
        document.form.birthday_day.focus();
        document.getElementById("errorBox").innerHTML = "select the birthday day";
        return false;
     }
     if (fyear == "") {
        document.form.birthday_year.focus();
        document.getElementById("errorBox").innerHTML = "select the birthday year";
        return false;
     }
        if(document.form.radiobutton[0].checked == false && document.form.radiobutton[1].checked == false){
                document.getElementById("errorBox").innerHTML = "select your gender";
             return false;
            }
        if(fname != '' && lname != '' && femail != '' && freemail != '' && fpassword != '' && fmonth != '' && fday != '' && fyear != ''){
            document.getElementById("errorBox").innerHTML = "form submitted successfully";
            }
         
}
</script>


<div id="description"></div>
<!--container start-->
<div id="container">
  <div id="container_body">
    <div>
      <h2 class="form_title">User Registration Form Demo</h2>
      <p class="head_para">Form Validated Using Javascript</p>
    </div>
    <!--Form  start-->
    <div id="form_name">
      <div class="firstnameorlastname">
       <form name="form" >
       <div id="errorBox"></div>
        <input type="text" name="Name" value="" placeholder="First Name"  class="input_name" >
        <input type="text" name="LastName" value="" placeholder="Last Name" class="input_name" >
       
      </div>
      <div id="email_form">
        <input type="text" name="Email" value=""  placeholder="Your Email" class="input_email">
      </div>
      <div id="Re_email_form">
        <input type="text" name="enterEmail" value=""  placeholder="Re-enter Email" class="input_Re_email">
      </div>
      <div id="password_form">
        <input type="password" name="Password" value=""  placeholder="New Password" class="input_password">
      </div>
      <!--birthday details start-->
      <div>
        <h3 class="birthday_title">Birthday</h3>
      </div>
      <div>
        <select name="birthday_month" >
          <option value="" selected >Month</option>
          <option value="1">Jan</option>
          <option value="2">Feb</option>
          <option value="3">Mar</option>
        </select>
        &nbsp;&nbsp;
        <select name="birthday_day" >
          <option value="" selected>Day</option>
          <option value="1">1</option>
          <option value="2">2</option>
          <option value="3">3</option>
          <option value="4">4</option>
          <option value="5">5</option>
        
        </select>
    
        <select name="birthday_year">
          <option value="" selected>Year</option>
          <option value="2013">2013</option>
          <option value="2012">2012</option>
          <option value="2011">2011</option>
         </select>
      </div>
      <!--birthday details ends-->
      <div id="radio_button">
        <input type="radio" name="radiobutton" value="Female">
        <label >Female</label>
        &nbsp;&nbsp;&nbsp;
        <input type="radio" name="radiobutton" value="Male">
        <label >Male</label>
      </div>
       <div>
        <p id="sign_user" onClick="Submit()">Sign Up </p>
      </div>
     </form>
    </div>
    <!--form ends-->
  </div>
</div>
<!--container ends-->

<style>
*{
    margin:0px;
    padding:0px;
    }
body{
    font-family:Tahoma, Geneva, sans-serif;
    }
#container{
    width:550px;
    background-color:rgba(250,250,252,.9);
    margin:auto;
    margin-top:10px;
    margin-bottom:10px;
    box-shadow:0 0 3px #999;
    }
#container_body{
    padding:20px;
    }
.form_title{
    font-size:35px;
    color:#141823;
    text-align:center;
    padding:10px;
    font-weight:normal;
    }
.head_para{
    font-size:19px;
    color:#99a2a7;
    text-align:center;
    font-weight:normal;
    }
#form_name{
    padding:25px 0 0 15px;
    }
.firstnameorlastname{
     margin-right:20px;
    }
.input_name{
    width:207px;
    padding:5px;
    font-size:18px;
    }
#email_form{
    clear:both;
    padding:15px 0 10px 0px;
    }
.input_email{
    width:434px;
    padding:5px;
    font-size:18px;
    }
#Re_email_form{
    padding:10px 0 10px 0px;
    }
.input_Re_email{
    width:434px;
    padding:5px;
    font-size:18px;
    }
#password_form{
    padding:10px 0 10px 0px;
    }
.input_password{
    width:434px;
    padding:5px;
    font-size:18px;
    }
.birthday_title{
    font-size:16px;
    color:#8b919d;
    font-weight:normal;
    padding:0 0 10px 0;
    }
select{
    padding:5px;
    }
#birthday{
    font-size:12px;
    color:#8b919d;
    padding-top:10px;
    }
#radio_button{
    padding:10px 0 0 0;
    }
#sign_user{
    font-size:14px;
    color:#FFF;
    text-align:center;
    background-color:#000000;
    padding:10px;
    margin-top:10px;
    cursor: pointer;
    }
#errorBox{
    color:#F00;
    }



</style>