How to get more information to debug 404 error

I have a website staged. Although everything seems to be displaying properly, opening developer tools shows I am getting two 404 errors (see pictures). I want to fix this error but I don't have much information. Is there some way to find out which specific element is causing the error? How should I go about debugging this?

Seek in the settings for a tab called Network.

Simply check the http status code for each of your elements from there.

This is a capture of the Firefox debugger, it works very similarly in other browsers dev tool.