http://newton.dm.unipi.it/cgi-bin/neodys/neoibo?objects:2006HZ51;main
the following link has vanished:
http://neo.jpl.nasa.gov/risk/2006hz51.html
Aha...
http://neo.jpl.nasa.gov/cgi-bin/db?name=2006+HZ51
It has been removed from the risk table, as impact has been ruled out.