<?php function is_blog () {
global $post;
$posttype = get_post_type($post );
return ( ((is_archive()) || (is_author()) || (is_category()) || (is_home()) || (is_single()) || (is_tag())) && ( $posttype == 'post') ) ? true : false ;
}?>
<?php if (is_blog()) { echo '<img class="main-img" src="http://webhosting4uk.co.uk/indianspiceschool/wp-content/themes/indianspiceschool/images/about.jpg" width="980" height="260" />'; } ?>