[TYPO3] error message after installation of css_styled_content

[toni]

hi there,

I  included css_styled_content but after this I always get following 
error message in the frontend:

Warning: exec() has been disabled for security reasons in 
/www/htdocs/w0062acc/web/t3lib/class.t3lib_stdgraphic.php on line 2378

Warning: Cannot modify header information - headers already sent by 
(output started at 
/www/htdocs/w0062acc/web/t3lib/class.t3lib_stdgraphic.php:2378) in 
/www/htdocs/w0062acc/web/tslib/class.tslib_fe.php on line 2614


does anybody now how to fix this problem?

cheers, toni