How to exclude a category from page

[ckarasiewicz]

I have a Wordpress custom page template created listing all of my blog posts. What I am trying to do is display a blog page, which lists all posts with 10 per page, with navigation, and exclude category 12, category 20, and category 50 from the list.

For some reason, I cannot get it to exclude these categories. I have even tried to exclude just one category and it still won't.

I am including the code that I am using for this page. If there is a better way to do this, I am open to it. What I am doing is showing the page title, the post title, an excerpt, and a read more link.

Thanks for your help.

Code:

PHP Code:

<?php  /*Template Name:Blog*/ ?>

<?php get_header(); ?>
<!--HEADER END HERE-->

<!--CONTENT STARTS HERE-->
<div class="modern-content-blog">
<div class="left">
<h2> <?php the_title(); ?> </h2>

<?php $paged = (get_query_var('paged')) ? get_query_var('paged') : 1; query_posts('cat=-12,'); 
$args = array( 'post_type' => 'post', 'posts_per_page' => 10, 'paged' => $paged );
$wp_query = new WP_Query($args);
while ( have_posts() ) : the_post(); ?>

    <h2 class="post-title"><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h2>
    Posted by: <?php the_author() ?> on <?php the_time('F jS, Y'); ?>
    <?php the_excerpt(); ?>
    <a href="<?php the_permalink(); ?>" title="Read the rest of <?php the_title(); ?>" class="button">Read the rest of this entry »</a> 

<div class="hr"></div>
<?php endwhile; ?>

<!-- PAGINATION STARTS HERE -->
<div class="button"><?php next_posts_link( '<< Older posts' ); ?></div> <div class="button"><?php previous_posts_link( 'Newer posts >>' ); ?></div>

</div>

<div class="right">

<ul>

<?php if ( !function_exists('dynamic_sidebar') ||  !dynamic_sidebar('social-sidebar') ||  !dynamic_sidebar('blog-sidebar') ) { ?>

<?php } ?>

</ul>

</div>
</div>

<!--FOOTER START HERE-->
<?php get_footer(); ?>