This is my first post and introduction to Cesium. I have experience with Google API in a limited capacity. So please be patient with my questions/ignorance.
I have a ESRI server behind my firewall local to my work. I'm using the following Tutorial to use ESRI REST to pull in the data. https://cesiumjs.org/2013/01/04/Cesium-Imagery-Layers-Tutorial/
The problem I noticed from the F12 Network window is an addition after the MapServer/tile/15/0/0 with a 404 error next to. Why is this occurring and how do I prevent it from happening?