Blockchain API: "Error Input String May Contain HTML"

[thonglor]

Hello all,

does anyone have an answer to that problem:

I'm trying to implement the Blockchain API receive_demo_php_demo. On their website https://blockchain.info/api/api_receive when I enter a Receiving Address and a Callback URL and then "Fire Test Callback" there always comes the red error message "Error Input String May Contain HTML". Why is that or what am I doing wrong?

Thanks for help!

Regards,
thonglor.