Help exclude categories from the blog feed

Hello there,
Im creating my own WordPress theme from scratch & wanting to know how i can exclude certain categories from a specific feed. At present i currently have the following on my blog page:

<?php query_posts('post_type=post&post_status=publish&posts_per_page=10&paged='. get_query_var('paged')); ?>
	<?php if( have_posts() ): ?>
        <?php while( have_posts() ): the_post(); ?>
	    	<div id="post-<?php get_the_ID(); ?>" <?php post_class(); ?>>
			<?php
				$attachment_id = get_post_thumbnail_id(); // attachment ID
				$image_attributes = wp_get_attachment_image_src( $attachment_id,'full' ); // returns an array
			?> 

        	<a href="<?php the_permalink(); ?>"></a>
            <h2><a class="blogposttitle" href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>

            <span class="meta"><?php the_time('F jS, Y'); ?>   &nbsp;/&nbsp;    Posted by <?php the_author_link(); ?> &nbsp;/&nbsp;
            <span class="comments">&nbsp;<?php comments_popup_link(__('0 comments','example'),__('1 comment','example'),__('% comments','example')); ?>
            </span>
            </span>

            <div class="dots"></div>
            <p><img src="<?php bloginfo('url'); ?>/imgresize.php?src=<?php echo $image_attributes[0]; ?>&h=200&w=800&q=100"></p> 

			<?php
			if (function_exists('has_excerpt') && has_excerpt())
			the_excerpt();
			else the_content('Read on...');?>

			<?php
            if (function_exists('has_excerpt') && has_excerpt()) { ?>
            <a href="<?php the_permalink() ?>" title="Continue Reading <?php the_title_attribute(); ?>...">Read more&raquo;</a>
			<?php  } ?>

            </div><!-- /#post-<?php get_the_ID(); ?> -->

             <?php endwhile; ?>

             <div class="navigation">
			<span class="newer"><?php previous_posts_link(__('? Newer','example')) ?></span> <span class="older"><?php next_posts_link(__('Older ?','example')) ?></span>
            </div><!-- /.navigation -->

			<?php else: ?>
            <div id="post-404" class="noposts">
            <p><?php _e('None found.','example'); ?></p>
            </div><!-- /#post-404 -->

			<?php endif; wp_reset_query(); ?>
            </div>

I have tried to play around with the query posts, but as i am not a php developer i keep getting errors. I have had a search through the forum yesterday but i cant relate the work to my own.

If anyone could give a few pointers i’d really appreciate it.

Thank you