<div class="solresim">
<?php if( get_post_meta($post->ID, "resim", true) ): ?>
<img src="<?php $values = get_post_custom_values("resim"); echo $values[0]; ?>" alt="<?php the_title(); ?>" />
<?php else: ?>
<img src="<?php bloginfo('template_directory'); ?>/rsm/resimyok.jpg" alt="<?php the_title(); ?>" />
<?php endif; ?>
</div>
<div class="yazi">
<?php the_content('...'); ?>
</div>

.solresim {
float:left;
margin: 0 auto;
overflow: hidden;
padding-right:8px;
margin-top:3px;
}
.solresim img {
width:100px;
height:100px;
}