CLC-2121 - Update 404 message with design from CLC-1025

https://jira.media.berkeley.edu/jira/browse/CLC-2121

Also

* Removed campanile image, since it's not used anymore
* Reorder CSS
* Fixes CLC-2200 - Lots of background images, e.g. the status popover, showing when screens load or are refreshed.
(It touches exactly the same lines of code)