psathish2 -6 Junior Poster in Training

warning error came..

Warning: session_start() [function.session-start]: Cannot send session cookie - headers already sent by (output started at D:\hshome\blackray\demo.blackraycreatives.com\gym\testing\final\employees.php:1) in D:\hshome\blackray\demo.blackraycreatives.com\gym\testing\final\captcha.class.php on line 21

Warning: session_start() [function.session-start]: Cannot send session cache limiter - headers already sent (output started at D:\hshome\blackray\demo.blackraycreatives.com\gym\testing\final\employees.php:1) in D:\hshome\blackray\demo.blackraycreatives.com\gym\testing\final\captcha.class.php on line 21

i have catcha.class.php include
captcha.class.php

class Capthcacode {

  function imagedisplay($rand) {

    $font = 'MAKEM___.ttf';
    $im = @imagecreate(80, 25) or die("Cannot Initialize new GD image stream");
    $background_color = imagecolorallocate($im, 255, 255, 255);
    $text_color = imagecolorallocate($im, 233, 14, 91);
    imagettftext($im, 16, 0, 10, 20, $text_color, $font, $rand);
    $path = "captcha/captcha.png";
    imagepng($im, $path, 9);
    imagedestroy($im);
    echo $path;

  }

  function initialize() {
      ob_start();
      session_start();
      if(!isset($_SESSION['captcha'])) {
        $rand = rand(10,254677);
        $_SESSION['captcha'] = $rand;
        session_register();

      }
  }

}

$captcha = new Capthcacode;

employees.php 

<?php

  include("captcha.class.php");
 $captcha->initialize();
ob_start();
   if(isset($_REQUEST['submit'])) {

      if( $_SESSION['captcha'] == $_POST['captchacode'] && !empty($_SESSION['captcha'] ) ) {

          echo 'Thank you.';

      } else {

          header("location:employees.php");

      }

  unset($_SESSION['captcha']);
  }

?>
<form method="post" action="employee.php" name="emp" onsubmit="return validate_form(this)" >
        <div class="textboxouter1">
          <div class="reumerinner">
            <table width="90%" border="0" cellspacing="0" cellpadding="0">
              <tr >
                <td width="33%" height="36" class="fontasall brdclr">Name :</td>
                <td width="55%"  class="pl8"><input type="text" id="status" name="txtnamefit"  /></td>
                <td width="12%">&nbsp;</td>
              </tr>
              <tr>
                <td height="36" class="fontasall brdclr">Name of Contact Person : </td>
                <td style="height: 28px"  class="pl8"><input type="text" id="status" name="txtcontact" /></td>
                <td style="height: 28px">&nbsp;</td>
              </tr>
              <tr>
                <td height="36" class="fontasall brdclr">Address and Location :</td>
                <td style="height: 32px"  class="pl8">&nbsp;
                  <input type="text" id="status" name="txtadd" /></td>
                <td style="height: 32px">&nbsp;</td>
              </tr>
              <tr>
                <td height="36" class="fontasall brdclr">Phone No :</td>
                <td style="height: 32px"  class="pl8">&nbsp;
                  <input type="text" id="status" name="txtphone" /></td>
                <td style="height: 32px">&nbsp;</td>
              </tr>
              <tr>
                <td height="36" class="fontasall brdclr">Email id :</td>
                <td  class="pl8">&nbsp;
                  <input type="text" id="status" name="email" /></td>
                <td>&nbsp;</td>
              </tr>
              <tr>
                <td height="36" class="fontasall brdclr">Looking for :</td>
                <td style="height: 32px"  class="pl8">&nbsp;
                  <textarea name="txtlookfor" cols="" rows="" onfocus="this.style.background = 'url(images/2.gif)';" onblur="this.style.background='url(images/1.gif)';" class="textarea1" ></textarea></td>
                <td style="height: 32px">&nbsp;</td>
              </tr>
              <tr>
                <td height="36" class="fontasall brdclr">Other Info :</td>
                <td  class="pl8">&nbsp;
                  <input type="text" id="status" name="txtother" /></td>
                <td>&nbsp;</td>
              </tr>
              <tr>
                <td height="43" class="fontasall brdclr">Word Verifications :</td>
                <td  class="pl8">&nbsp;
                  <input type="text" name="captchacode" id="captchacode" />
                  <img src="<?php $captcha->imagedisplay("$_SESSION[captcha]");?>" alt="captcha"  /></td>
                <td>&nbsp;</td>
              </tr>
              <tr>
            </table>

the text box enter the value and captcha image not same ,, but execute the page.