This error is quite common and it generally means it can't find the file it's looking for, but I can see the file in the directory?!
Full error:
Warning: require(/home/coinsfut/public_html/files/core.php) [function.require]: failed to open stream: No such file or directory in /home/coinsfut/public_html/new/index.php on line 4
line 4 says:
require $_SERVER['DOCUMENT_ROOT']. "/files/core.php";
the site is hosting in /new
any ideas?