To remove the white space, look at your theme's header.php and remove any white space you see at the top of the file. It should ideally only contain <?php on the first line of the document and no white space between the closing ?> and your DOCTYPE declaration, e.g.
<?php/** * header.php */?><!DOCTYPE html><!-- rest of file... -->
Looking at a content page on your site, I see there's no closing </body> or </html> which leads me to believe that your template is missing a get_footer(); call or footer.php is incomplete.