HTML

<form name=registerForm action=/user/register.cgi method=post onsubmit=validateRegisterForm()>

  <table>

    <tbody>

      <tr>

        <td><input type=text name=firstname placeholder=First Name></td>

      </tr>

      <tr>

        <td><input type=text name=lastname placeholder=Last Name></td>

      </tr>

      <tr>

        <td><input type=email name=email placeholder=Email></td>

      </tr>

      <tr>

        <td><input type=password name=password placeholder=Password></td>

      </tr>

      <tr>

        <td><input type=password name=confirmPassword placeholder=Confirm Password></td>

      </tr>

      <tr>

        <td><input type=submit value=Register Details></td>

      </tr>

    </tbody>

  </table>

</form>

Javascript

function validateRegisterForm(){

var fname=document[registerForm][firstname].value;

var lname=document[registerForm][lastname].value;

var email=document[registerForm][email].value;

var atpos=email.indexOf(@);

var dotpos=email.lastIndexOf(.);

var pass=document[registerForm][password].value;

var passlen = pass.length;

var confpass=document[registerForm][cofirmPassword].value;



if (fname==null || fname==)

  {

  alert(Please enter a First Name!);

  return false;

  }

else if (lname==null || lname==)

  {

  alert(Please enter a Last Name!);

  return false;

  }

else if (email==null || email==)

  {

  alert(Please enter a email!);

  return false;

  }

else if (atpos<1 || dotpos<atpos+2 || dotpos+2>=x.length)

  {

  alert(Please enter a valid email address!);

  return false;

  }

else if (pass==null || pass==)

  {

  alert(Please enter a Password!);

  return false;

  }

else if (6<=passlen<=15)

  {

  alert(Password needs to be to have a lenght of 6-15!);

  return false;

  }

else if (pass!=confpass)

  {

  alert(Passwords do not match!);

  return false;

  }

}