<div class="konuiciresim">
						  	<?php if ( has_post_thumbnail() ) the_post_thumbnail( 'single-post-thumbnail' );
									else echo '<img src="' . get_bloginfo( 'stylesheet_directory' ) . '/arayuzweb.jpg" title="<?php the_title(); ?>" />';
							?>
						</div>

.konuiciresim img {float:left; height:300px; width:48%; margin: 2px 5px 2px 2px;}