models.py

from django.db import models
from django.contrib.auth.models import User

# Create your models here.
class Site(models.Model):
	user = models.ForeignKey(User)
	site = models.CharField(max_length=255)

	def __unicode__(self):
		return self.site

class Inventory(models.Model):
	site = models.ForeignKey(Site)
	date = models.DateField()
	impressions = models.IntegerField(default=0)
	clics = models.IntegerField(default=0)
	ctr = models.FloatField(default=0)
	cpc = models.FloatField(default=0)
	ecpm = models.FloatField(default=0)
	earnings = models.FloatField(default=0)

	def __unicode__(self):
		return str(self.date)+' - '+str(self.site)

Liste les stats du site si il appartient à l'user loggé :
list_stats = Inventory.objects.all().filter(user=user).order_by('date') ?

Réponse =
list_stats = Inventory.objects.all().filter(site__user=User).order_by('date') ?