SuperMAG,
For example you have this line in your config.php:
$cookie_seed = 'xxxxxxxx';
Then replace it with something like this:
$cookie_seed = 'xxxxxxxx275be39a';
or this:
$cookie_seed = '275be39axxxxxxxx';
or this:
$cookie_seed = '275be39fewqhf342qw4132oh423fdiuqwha';
or this:
$cookie_seed = '21212121dsafasxxxxxxxxfdsffafa3123123';
I hope it's clear now.
Thanks guys for the update!