**WARNING** Authentication/Security Keys in wp-config file missing after upgrading to 3.0
If you have recently upgraded to 3.0, please open your config file and get new security keys. WP 3.0 uses a different set of security keys than prior versions. It uses the same set as WP MU does, so you will have to get new ones.
You will find it below the database information
Copy and paste the link highlighted below into your browser address bar. You will see something like the above , but with the actual keys.
This is what your config file should look like once you copied the keys. then you just save and close in the upper right corner.