Styling a Post Thumbnail

<div class="griditemleft">
<?php
$my_query = new WP_Query( 'posts_per_page=9&cat=6' );
?>
<?php if ( $my_query->have_posts() ) {
       while ( $my_query->have_posts() ) {
	$my_query->the_post();
	echo get_the_post_thumbnail($id, 'thumbnail', array('class' => 'alignleft {margin-left: 30px; display: block;}', 'alt' => 'alttext'));
	}
       }
?>
<?php
   wp_reset_postdata();
?>
</div>

Here is the css for griditemleft:
.griditemleft{
	float: left;
	width: 600px;
	margin: 10px 40px 40px 0;
	}