problem with float

I have the following code:
<div class="sidebar">
...
</div>
<div class="content">
<div class="youarehere">
<span class="left bread"><?php breadCrumb($page_URI); ?></span>
<span class="right date"><?php include 'php/date_printout.php';?></span>
</div>
<br class="clear">
<?php if($page_URI_content!="") {require_once ("$page_URI_content");}?>
<div class="spacer"></div>
</div>

on my website with http://www.matthiaspospiech.de/links/allgemein/ you can see the problem: The content is below the sidebar.
If I take out the <br class="clear"> then the header (here 'Sonstiges')
appears directly after "aktuelle Seite" in the left part of youarehere

left and right are defined as this
.left {
float: left;
text-align: left;
}

.right {
float: right;
text-align: right;
}

Hope the problem is clear.
Matthias