The folder containing your subdomain (probably /public_html/m ) should have permissions set to 0755
Further , if your .htaccess file in that directory (or in public_html if you do not have one in /m ) has Options -Indexes , you must have an index.html or index.php ( the options setting keeps Litespeed from displaying an "Index of" page when there is no 'DirectoryIndex' page, ie index.php, index.html...)