widget after page list in sidebar

when I add widget my sidebar loose css propiertis.
I would like to insert widget after my sidebar:
This is may sidebar code:

<div id=”sidebar”>
<?php if ( !function_exists(‘dynamic_sidebar’)
|| !dynamic_sidebar() ) : ?>

<ul class=”pagenav”>
<?php wp_list_pages(‘depth=1&title_li=’); ?>

<h1>PRODOTTI</h1>

<div id=”searchdiv”>
<form id=”searchform” method=”get” action=””>
<label for=”s”>cerca nel sito:</label>
<input type=”text” name=”s” id=”s” size=”20″/>
<input type=”submit” name=”sbutt” value=”Vai” />
</form>
</div>

<?php
wp_list_categories(‘orderby=name&title_li=’); ?>

<?php endif; ?>
</div>

THIS IS MAY FUNCTIONS.PHP CODE:

<?php
if ( function_exists(‘register_sidebar’) )
register_sidebar();
?>