The Target Of The Callback Could Not Be Found

What you're seeing is a JavaScript message about a failed attempt to execute some code (the "callback"). Coders put messages like these in their site to help them diagnose problems while they build them. When you publish the site, it's considered best practice to turn these debugging messages off so that visitors don't see them. Clearly, this hasn't happened.

Generally speaking, this site uses some sloppy and complex JavaScript code, and it's unsurprising that there are some user-facing bugs. Oliver, the .js string might be in a nested lib somewhere... there's a ton of code here (over 20 external js includes, and some repeats).

If you want, you can poke around in IE settings and try to turn off JavaScript warnings, but I would otherwise ignore this message. It's just an awkwardly made website.