Problem with theme…

Hello. I create theme for WordPress but I have errors when I try save enything… I have error content: Warning: Cannot modify header information – headers already sent by (output started at /homepages/44/d347704352/htdocs/wp_test/wp-content/themes/web/functions.php:1) in /homepages/44/d347704352/htdocs/wp_test/wp-includes/pluggable.php on line 881

Following codes of the files:

index.php

<?php get_header(); ?>
<?php get_sidebar(); ?>
<?php get_footer(); ?>

footer.php

<div class="clear"></div>

<div id="footer">

<div id="linia"></div>
<div class="clear"></div>
<p>Copyright ? xx.<br>All rights reserved.</p>

</div> <!-- end footer -->

</div> <!-- end page -->
<?php wp_footer(); ?>
</body>

</html>

header.php

[code moderated - use the pastebin for any code over the forum limit of 10 lines]

sidebar.php

[code moderated - use the pastebin for any code over the forum limit of 10 lines]

functions.php

<?php

if ( function_exists('register_sidebar') )
register_sidebar(array(
'name' => 'Right Sidebar',
'before_widget' => '<li id="%1$s" class="%2$s">',
'after_widget' => '</li>',
'before_title' => '<h2>',
'after_title' => '</h2>',
));

?>

style.css

[CSS code moderated - just post a link to your site]

Please help because I do not know what could be wrong...