CSS import error

hi . i'm new to typolight when i try to import some css file as told in typolight tutorial i get this error:

Fatal error: Uncaught exception Exception with message Cannot create file "xNavigation.css" thrown in /home/lxsameer/www/typolight-2.7.2/system/libraries/File.php on line 107

#0 /home/lxsameer/www/typolight-2.7.2/system/modules/backend/StyleSheets.php(135): File->__construct('xNavigation.css')
#1 /home/lxsameer/www/typolight-2.7.2/system/modules/backend/StyleSheets.php(76): StyleSheets->writeStyleSheet(Array)
#2 /home/lxsameer/www/typolight-2.7.2/system/modules/backend/StyleSheets.php(612): StyleSheets->updateStyleSheet('5')
#3 /home/lxsameer/www/typolight-2.7.2/system/modules/backend/Backend.php(169): StyleSheets->importStyleSheet(Object(DC_Table), 'tl_style_sheet', Array)
#4 /home/lxsameer/www/typolight-2.7.2/typolight/main.php(99): Backend->getBackendModule('css')
#5 /home/lxsameer/www/typolight-2.7.2/typolight/main.php(294): Main->run()
#6 {main}

whats wrong ? when i create a page it has no css.

and how can i install a template ? is there any free template around ? should i create header and footer by hand ?