Código PHP:
<?php
$counter = 1;
while($noticia = next($rhe)){
if($counter == 1){
$counter++; ?>
<div class="TeaserBig" onmouseover="activate_teaser(this)"></div>
<?php }else{ ?>
<div class="TeaserSmall" onmouseover="activate_teaser(this)"></div>
<?Php }
} ?>