i never had a problem on installing this before but this time i did something wrong, can anyone help?

Warning: main(includes/application_top.php) [function.main]: failed to open stream: Permission denied in /public_html/artwork/index.php on line 26

Fatal error: main() [function.require]: Failed opening required 'includes/application_top.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /public_html/artwork/index.php on line 26

Warning: main(includes/application_top.php) [function.main]: failed to open stream: Permission denied in /public_html/artwork/index.php on line 26

Fatal error: main() [function.require]: Failed opening required 'includes/application_top.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /artwork/index.php on line 26