Warning: require_once(sol.php) [function.require-once]: failed to open stream: No such file or directory in /home/....../public_html/index.php on line 16

Fatal error: require_once() [function.require]: Failed opening required 'sol.php' (include_path='.:/usr/lib/php:/usr/local/lib/php') in /home/......./public_html/index.php on line 16