RPC failed 32700 Invalid JSON

Today i was editing one of my bloggers template and this Error message upper on the lower position. What is the meaning of this pop up message "RPC failed 32700 Invalid JSON."

Have a look at the screenshot picture below.

JSON-RPC is a remote procedure call protocol encoded in JSON. It is a very simple protocol (and very similar to XML-RPC), defining only a handful of data types and commands. JSON-RPC allows for notifications (info sent to the server that doesn't require a response) and for multiple calls to be sent to the server which may be answered out of order.