This only happens on Google Chrome and Chromium with a fresh install of Laravel.
The page shows blank and in the console it says:
(failed) net
Had the same problem on a Ubuntu 14.04 Vagrant box running nginx. The site is a Laravel 5 that one day surprisingly started throwing those errors.
After reading this comment: https://github.com/barryvdh/laravel-debugbar/issues/262#issuecomment-74385850
I've checked my /var/log/nginx/vagrant.com-error.log.1 and saw:
[crit] 1020#0: *774 open() "/var/lib/nginx/fastcgi/3/03/0000000033" failed (13: Permission denied) while reading upstream, client: 192.168.56.1, server: 192.168.56.102.xip.io, request: "GET /_debugbar/assets/javascript?1423122680 HTTP/1.1", upstream: "fastcgi://127.0.0.1:9000", host: "my-host", referrer: "http://url/that/fails"
Double-checked my Vagrant box nginx lib directory permissions ll /var/lib/
drwxr-xr-x 7 root root 4096 feb 9 11:28 nginx/
... where internally was using www-data user: ll /var/lib/nginx/
drwx------ 12 www-data root 4096 may 5 13:32 fastcgi/
So I ran:
chown -R www-data:www-data /var/lib/nginx
And the error in Chrome disappeared.
Just posting here to notice the solution, even all the credits should go to the linked original comment.