Exclude category from index page

Hello,

I use a static homepage and another page for my news. Now I want to exclude a certain category, but code below is not working. What do I do wrong?

<?php query_posts($query_string . '&cat=-14'); ?>
<?php if (have_posts()) : while (have_posts()) : the_post(); ?>

14 is the category which I want to remove. (Is it also possible to add a slug?)