Domain Mapping, why does this file load on the front end?

I'm trying solve some page load speed issues, and there are 2 flies in my ointment to getting a decent speed. One is a 3 second wait time for my server to load up the domain, which I think is more server related than anything else. The second though is that this file:


loads up on the front end of a mapped domain and it also happens to have a 3 second load time as well.

My questions are:

Should this file even be loading on the front end?

Why does it take 3 seconds to load?

Could it possibly have something to do with the 3 sec. wait on loading my domain?