Header Problem though header is not sent before
<p><strong>I know before sending their should not be any printing statement on the screen.</strong> and I haven't did that in my code. Their is no echo statement no print statement.</p>

<blockquote>
  <p><strong>warning</strong> Cannot modify header information - headers already sent by (output started at /home/oxfordmo/public_html/php/user/header.php:18) in /home/oxfordmo/public_html/php/user/index.php on line 21</p>
</blockquote>

<p>Its showing error in header file.</p>

<p>Indexfile line 21</p>

<blockquote>
  <p>header("location:user.php?f=".base64_encode($_SESSION['firstname'])."&amp;l=".base64_encode($_SESSION['lastname']));</p>
</blockquote>

<p>and header file 15-20</p>

<pre><code>&lt;div id="wrapperheader"&gt;
  &lt;div id="menu"&gt;
   &lt;ul&gt;
    &lt;li class="active"&gt;&lt;a href=""&gt;Company&lt;/a&gt;&lt;/li&gt;
    &lt;li&gt;&lt;a href=""&gt;Services&lt;/a&gt;&lt;/li&gt;
    &lt;li&gt;&lt;a href=""&gt;Gallery&lt;/a&gt;&lt;/li&gt;
</code></pre>
