Wordpress meta tag

<title><?php global $page, $paged; wp_title( '&laquo;', true, 'right' ); bloginfo( 'name' ); if ( $paged >= 2 || $page >= 2 ) echo ' &raquo; ' . sprintf( __( 'Page %s' ), max( $paged, $page ) ); ?></title>

<meta name="description" content="<?php set_meta_description(); ?><?php if ( $paged < 2 ) { } else { echo (' Pagina '); echo ($paged); } ?>" />

<?php if (is_single()&& has_post_thumbnail()) { ?>

  <link rel="image_src" href="<?php $src = wp_get_attachment_image_src( get_post_thumbnail_id($post->ID), array( 150, 150 ), false, '' ); echo $src[0]; ?>" />

<?php }else{ ?>

  <link rel="image_src" href="<?php bloginfo('siteurl'); ?>/wp-content/themes/MyTheme/images/preview.jpg" />

<?php } ?>