URL mysite.com/?author=2 leads to blank page

It’s a theme I constructed from scratch.

I used this to help me:

http://themeshaper.com/2012/10/23/developing-your-theme-sense-tutorial-2/

Thanks.

I just created author.php which contains the following:

<?php get_header(); ?>
<div class="row">
    <div class="large-8 columns">
      <?php
        $author=$_GET['author'];
        echo $author;

      ?>

    </div><!-- #row content .site-content -->
  <?php get_sidebar(); ?>
</div><!-- #primary .content-area -->
<?php
  get_footer();
?>

The page gives me “2”, so that’s great. I can get a list of each author’s output from that….