Adding a max-width to Posts!

Hello I’m using wordpress and I’ve just got my “latest post” to show on my homepage (www.skerwin.co.uk) but I need to set a max image size for the bit displayed on my website, the php used to display my post is:

<?php
// Include WordPress?
define(‘WP_USE_THEMES’, false);
require(‘./blog/wordpress/wp-load.php’);
query_posts(‘showposts=1’);
?>

<?php while (have_posts()): the_post(); ?>
<span class=”RED”><?php the_title(); ?></span>
<?php the_content(); ?>?
<p>“>Read more…</p>
<?php endwhile; ?>

Which is just pasted into a div tag, any help with setting a max image width so it doesn’t ruin my layout when I post pictures would be much appreciated, a swift response would also be greatly appreciated!