I am a beginner in Symfony 3.

I've installed it and when i go to <http://localhost/Symfony/web/app_dev.php>
the page is displaying then there is a javascript confirm box with the message "An error occured while loading the web debug toolbar (404:Not Found). Do you want to open the profiler?"

Even if i go to <http://localhost/Symfony/web/app_dev.php/test> i have a 404 error page, but it is not the Symfony 404 page.

I am on Ubuntu and Nginx.

I have tried differents things but nothing were correct for me.

Could you give me a hand on that so I don't have this confirm box and can go to others pages ?

Thanks.

UPDATE:
In the var/logs/dev.log i have this message : 

```
[2017-07-18 11:00:39] request.INFO: Matched route "homepage". {"route":"homepage","route_parameters":{"_controller":"AppBundle\\Controller\\DefaultController::indexAction","_route":"homepage"},"request_uri":"http://localhost/Symfony/web/app_dev.php/","method":"GET"} []
[2017-07-18 11:00:39] security.INFO: Populated the TokenStorage with an anonymous Token. [] []

```

Edit : 

I restart the install with the version 3.3.5

I did these line and it worked a little bit better : 

```
sudo mkdir -p /usr/local/bin
sudo curl -LsS https://symfony.com/installer -o /usr/local/bin/symfony
sudo chmod a+x /usr/local/bin/symfony

```

I had to change the composer.json too with these lines : 

```
"autoload": {
        "psr-4": {
            "": "src/"
        },

```

Here my nginx config : 

```
server {
    listen 80 default_server;
    listen [::]:80 default_server;
    root /var/www/html;

    index index.html index.htm index.nginx-debian.html;

    server_name localhost;

    location / {
                try_files $uri $uri/ /index.php?$args /app.php$is_args$args;
    }

# start symfony
location ~ ^/(app_dev|config)\.php(/|$) {
        fastcgi_pass unix:/var/run/php5-fpm.sock;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;
        include fastcgi_params;
        fastcgi_param SCRIPT_FILENAME $realpath_root$fastcgi_script_name;
        fastcgi_param DOCUMENT_ROOT $realpath_root;
    }
# end symfony

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass 127.0.0.1:9000;
    }
}

```

But I still have the 404 error page for any pages, even for a bundle that I have generated.

Any ideas ?