changing settings.php caused CRASH

I installed CK editor in drupal and it worked fine.

After that I also installed CK-finder. The text I got in Drupal was that it was not safe to use finder and that I had to do something in settings.php.

Then I checked closely the Read-Me-Manual that comes with CK-editor. It is written like this:

6. Locate file named settings.php inside your drupal directory
(usually sites/default/settings.php) and set $cookie_domain variable to the
appropiate domain (remember to uncomment that line). If you don't do this,
CKFinder may show an information that the connector is disabled.

So what I did was to enable writing permission in settings.php and then I changed the content of the file like this:
before change:
# $cookie_domain = 'example.com';

After change:
//# $cookie_domain = 'example.com';
# $cookie_domain = 'www.focusmetacoaching.se';

it caused the whole thing to crash. I tried to take away the "www." but nothing helped.
then I changed it back to its original text, but now I still get the same message when I try to open my site:

Fatal error: Call to undefined function check_markup() in /home/web78036/domains/focusmetacoaching.se/public_html/modules/node/node.module on line 1044

It seems like the problem message refers to something in the node.module, but I haven´t changed anything there. Now I don´t know what to do. How can I get the things to work?

thanks for your help
Henrik