I created a password lock on My Galaxy Note 3 with the Android Device Manager web site.
How can I cancel it or administer it? (I have reduced the hassle a bitb y creating a simple password on the website)
When locking a device using Android Device Manager it replaces the previous "Screen lock" with a password. Once you have entered the password you can follow these steps to remove/replace the screen lock:
Steps performed on a Nexus 5, they might be slightly different on other devices
The title is a bit confused. @bmdixon's answer works for the situation that you want to delete the password in the case you knew the password. However, in most of the cases we want to remove the password we just forgotten. My answer is based on this.
For Android 4.4 and below, you can sign in Google account to reset the password.
For Android 5.0 and above, you can set a tmp password for the phone via Android Device Manager service. And use the tmp password to unlock the phone.
If you used Samsung device, then you can reset the password with Find My Mobile service.
Added: Here is a detailed guide on how to reset android password in 3 different ways. Best for beginners.