Is it possible to move /var/www folder by another one as /media/pi/USBSTICK/www ?

I there,
I am a french newbie user of Nginx.
My web site works perfectly when I use /var/www folder.
But, I use a Raspberry Pi to heberge it.
As you known, Rapsberry PI is a nano PC that use MicroSD card (8GB for my case).
I would like to use a harddisk or another USBStick to stock and partage photos and videos throught my web site.
Is it possible to move /var/www folder by another one as /media/pi/USBSTICK/www ?
I have modify "sites-available/default" file to take this changes. But firefox, or IceWasel displayes "403 error page".
Maybe is it forbidden to use /media/pi/USBSTICK/www folder...