website wont open Fatal error: require()

cant open my website.
can’t even log in to http://jozefibarr.com/wp-admin/

webstie jozefibarr.com

says::

Fatal error: require() [function.require]: Failed opening required ‘/home/content/26/13464226/html/wp-includes/class-wp-roles.php’ (include_path=’.:/usr/local/php5_3/lib/php’) in /home/content/26/13464226/html/wp-settings.php on line 125

can someone guide me as to how i can resolve this?

(i have the impression that i must go to my godaddy file manager. but then i don’t know which folder to open and where to look)

thanks much

j