Version: vBulletin 4.0.3
Remove following code in navbar template
<vb:if condition="$show['notices']">
<form action="profile.php?do=dismissnotice" method="post" id="notices" class="notices">
<input type="hidden" name="do" value="dismissnotice" />
<input type="hidden" name="s" value="{vb:raw session.sessionurl}" />
<input type="hidden" name="securitytoken" value="{vb:raw bbuserinfo.securitytoken}" />
<input type="hidden" id="dismiss_notice_hidden" name="dismiss_noticeid" value="" />
<input type="hidden" name="url" value="{vb:raw return_link}" />
<ol>
{vb:raw notices}
</ol>
</form>
</vb:if>
Don't want to remove forever:
The Notices Manager
Admin CP > Notices > Notices Manager
(http://www.vbulletin.com/docs/html/notices)