Karl Heinz on "Erros message"

Hi.
I installed latest version of WordPress oon also latest version of Xampp. Everything worked fine. Installation of the theme and plugins.
Also all functions work fine. I´m still a novice in WordPress and don´t know how everthing works. But since the second login I get the following error message shown in the picture below.
Is there a way to fix it or to remove this message?
What is the motive to receive this Waing message?
Thanks for any help.

http://imgur.com/rtxGEqQ

Please try again.

All my logins show this message. Updated also first post showing now the error message.