<div style="float:left; margin-right:10px;" class="Small-Landscape-image">
<?php $resim = get_post_meta($post->ID,'resim', true); 
if($resim != "") {  ?>
<a href="<?php the_permalink() ?>"><img src="<? echo strtolower($resim); ?>"></a>
<?php }else{ ?>
<a href="<?php the_permalink() ?>"><img src="http://www.siteniz.com/defaultresim.jpg"></a>
<?php } ?> 
</div>