Fatal error,

The script show this message when I make the first step to upload one file:
Fatal error: Directory /home/mklmedia/public_html/videotube/include/htmlpurifier/HTMLPurifier/DefinitionCache/Serializer/HTML not writable, please chmod to 777 in /home/mklmedia/public_html/videotube/include/htmlpurifier/HTMLPurifier/DefinitionCache/Serializer.php on line 160

Anybody can help me? Its the first tIme than I read one message like this.

Navigate to that directory that it is showing you using your FTP program, then right click on it and choose CHMOD. Change it to 777.

If you can't get it fixed, please open a Support ticket with your site admin and FTP login details.

Thanks,