You were missing at least one }. I added a few others for clarity. Also, it appears you have quite a few incomplete html tags (most of your <font> tags have no </font> to close them, there's a <div> with no </div>), you might want to clear those up to keep your pages from displaying incorrectly.
<?php
include("design/header.php");
require("connect.php");
//register code
if ($_POST['submit'])
{
//grab summited data
$fistname = $_POST['firstname'];
$lastname = $_POST['lastname'];
$username = $_POST['username'];
$password = $_POST['password'];
$password_repeat =$_POST['password_repeat'];
$dob_day = $_POST['dob_day'];
$dob_month = $_POST['dob_month'];
$dob_year = $_POST['dob_year'];
$gender = $_POST['gender'];
if (
$firstname&&
$lastname&&
$username&&
$password&&
$password_repeat&&
$dob_day&&
$dob_month&&
$dob_year&&
$gender) {
//validate
if (strlen($firstname)>25 || strlen($lastname)>25 || strlen($username)>25) {
echo "Firstname , Lastnam Or Username Must Be In 25 Characters";
} else {
//check password
if (strlen($password)>25||strlen($password)<6){
echo "Password Must Between In 6 To 25 Character Long.!";
} else {
echo "Ok";
}
}
} else
echo "Missing Field .! Please Fill Out All Fields.";
}
?>
<form action='signup.php' method='POST'>
<br>
<br>
<br>
<br>
<br>
<p>
<table width='60%'>
<tr>
<td width='40%' align='right'>
<font size='2' face='Constantia'>Firstname:
</td>
<td>
<input type='text' name='firstname' maxlenght='25'>
</td>
</tr>
<tr>
<td width='40%' align='right'>
<font size='2' face='Constantia'>Lastname:
</td>
<td>
<input type='text' name='lastname' maxlenght='25'>
</td>
</tr>
<tr>
<td width='40%' align='right'>
<font size='2' face='Constantia'>Username:
</td>
<td>
<input type='text' name='username' maxlenght='25'>
</td>
</tr>
<tr>
<td width='40%' align='right'>
<font size='2' face='Constantia'>Password:
</td>
<td>
<input type='password' name='password' maxlenght='25'>
</td>
</tr>
<tr>
<td width='40%' align='right'>
<font size='2' face='Constantia'>Repeat Password:
</td>
<td>
<input type='password' name='password_repeat' maxlenght='25'>
</td>
</tr>
<tr>
<td width='40%' align='right'>
<font size='2' face='Constantia'>Date Of Birth:
</td>
<td>
<input type='text' name='dob_day' maxlenght='2' size='1' value='DD'> / <input type='text' name='dob_month' maxlenght='2' size='1' value='MM'> / <input type='text' name='dob_year' maxlenght='4' size='3' value='YYYY'>
</td>
</tr>
<tr>
<td width='40%' align='right'>
<font size='2' face='Constantia'>Gender:
</td>
<td>
<select name='gender'>
<option>Male</option>
<option>Female</option>
</select>
</td>
</tr>
</table>
<div align='right' width='40%' style="width: 356px; height: 30px"><input type='submit' name='submit' value='Sign Up' >
</form>
<?php
include("design/footer.php");
?>