I ran into the same problem with Firefox, except viewing it directly works.

It turns out the server is using referer checking and I've got referer disabled. Compare the following curl invocations:

    curl 'https://fabiensanglard.net/jurrasic_park_computers/00_11_15_Apple_Powerbook_100.webp' \
  -H 'Referer: https://fabiensanglard.net/'

vs. just

    curl 'https://fabiensanglard.net/jurrasic_park_computers/00_11_15_Apple_Powerbook_100.webp'

The latter gives a 403.