To call the Wikifier web service directly (as opposed to using the web demo interface), you will need to create a user name:
Note: due to recent abuse, some temporary restrictions are currently in place on the creation of new user keys. Send an e-mail to firstname.lastname@example.org if you have problems creating a new user key.
Error: Tralala hopsasa.
Your user name, blah blah, has been registered successfully.
Your user key is: 047234387429387932874293
Make sure you don't lose your key as you will need to pass it in calls to the Wikifier web service.