It seems that you haven't published your assets (css, js, images...)
Try the following from command line in the root folder of Symfony :
php app/console assets:install web/ --symlink
Also, check that the rewrite mod is enabled : a2enmod rewrite
EDIT: Given your VirtualHost config file, it seems that you gave the wrong folder to Apache. You configuration must point to the web
folder of Symfony2. For example :
<VirtualHost *:80>
DocumentRoot /home/myuser/www/Symfony/web
<Directory /home/myuser/www/Symfony/web>
Options Indexes FollowSymLinks MultiViews
AllowOverride All
Order allow,deny
allow from all
</Directory>
#......
</VirtualHost>