Ok, if "Erwartet" means expected, then therefore there is a missing closing bracket ')' on a script on that page. Therefore this breaks JavaScript, therefore things like tabs (that rely on JavaScript) don't work. Thus you have some JavaScript on that page that needs to be fixed. So look at / click on the error and attempt to decipher what that script is and take things from there.
Themes
Boost Theme in Internet Explorer 11
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