Omeka has encountered an error

InvalidArgumentException

Could not find file css/.css!

InvalidArgumentException: Could not find file css/.css! in /web/images.bowdoin.edu/new-omeka/application/libraries/globals.php:1288
Stack trace:
#0 /web/images.bowdoin.edu/new-omeka/application/libraries/globals.php(1247): web_path_to('css/.css')
#1 /web/images.bowdoin.edu/new-omeka/application/libraries/globals.php(1193): src('css/.css', 'css', 'css', '2.8')
#2 /web/images.bowdoin.edu/new-omeka/application/libraries/globals.php(1093): css_src(NULL, 'css', '2.8')
#3 /web/images.bowdoin.edu/new-omeka/themes/libarch/common/header.php(29): queue_css_file(NULL)
#4 /web/images.bowdoin.edu/new-omeka/application/libraries/Omeka/View.php(114): include('/web/images.bow...')
#5 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/web/images.bow...')
#6 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/View/Helper/Partial.php(109): Zend_View_Abstract->render(NULL)
#7 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/View/Abstract.php(349): Zend_View_Helper_Partial->partial('common/header.p...', Array)
#8 /web/images.bowdoin.edu/new-omeka/application/libraries/globals.php(1665): Zend_View_Abstract->__call('partial', Array)
#9 /web/images.bowdoin.edu/new-omeka/application/libraries/globals.php(1679): common('header', Array)
#10 /web/images.bowdoin.edu/new-omeka/themes/libarch/items/browse.php(3): head(Array)
#11 /web/images.bowdoin.edu/new-omeka/application/libraries/Omeka/View.php(114): include('/web/images.bow...')
#12 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/View/Abstract.php(888): Omeka_View->_run('/web/images.bow...')
#13 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(912): Zend_View_Abstract->render(NULL)
#14 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(933): Zend_Controller_Action_Helper_ViewRenderer->renderScript('items/browse.ph...', NULL)
#15 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Controller/Action/Helper/ViewRenderer.php(972): Zend_Controller_Action_Helper_ViewRenderer->render()
#16 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Controller/Action/HelperBroker.php(277): Zend_Controller_Action_Helper_ViewRenderer->postDispatch()
#17 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Controller/Action.php(527): Zend_Controller_Action_HelperBroker->notifyPostDispatch()
#18 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Controller/Dispatcher/Standard.php(308): Zend_Controller_Action->dispatch('browseAction')
#19 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#20 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Application/Bootstrap/Bootstrap.php(105): Zend_Controller_Front->dispatch()
#21 /web/images.bowdoin.edu/new-omeka/application/libraries/Zend/Application.php(384): Zend_Application_Bootstrap_Bootstrap->run()
#22 /web/images.bowdoin.edu/new-omeka/application/libraries/Omeka/Application.php(73): Zend_Application->run()
#23 /web/images.bowdoin.edu/new-omeka/index.php(23): Omeka_Application->run()
#24 {main}