Comments by Steve Yates (Top 1 by date)

The [here] link is 404. Microsoft's site: https://support.microsoft.com/en-us/kb/2915218#bookmark-appendixa
Note their comment, "There are many web sites that will generate a < machinekey > element for you with the click of a button. Never use a < machinekey > element that you obtained from one of these sites."
To use, copy the PowerShell function into a script, add a line "Generate-MachineKey" at the bottom (they forgot to call the function) and run it.