title: ERROR :- One or more models did not validate
body: <p>I am new in django. 
  My question is that:- I got an error(below describe) when apply syncdb</p>
  
  <blockquote>
    <p>ERROR: One or more models did not validate:</p>
  </blockquote>
  
  <p>my models.py</p>
  
  <pre><code>     class practicalArea:
          practical_area = models.CharField(max_length=25)
  
          class Meta:
              db_table = 'practical_area'
  
          def __unicode__(self):
              return self.practical_area
  
  
  class Profile(models.Model):
          auth_user_id = models.ForeignKey(User, related_name='userProfile')
          address = models.TextField(blank=True)        
          state = models.CharField(max_length=20)
          practical_area = models.ForeignKey('practicalArea', related_name='practical_Area')        
          company = models.CharField(max_length=40)     
          photo = models.CharField(max_length=250)
          created_date = models.DateTimeField()
          modify_date = models.DateTimeField()
  
  
          class Meta:
              db_table = 'adminPanal_profile'
  
  
          def save(self):
              if self.created_date == None:
                  self.created_date = datetime.now()
              self.modify_date = datetime.now()
              super(Profile, self).save()
  </code></pre>
  
  <p>if i change "practical_area = models.ForeignKey('practicalArea', related_name='practical_Area')" to "practical_area = models.ForeignKey(practicalArea, related_name='practical_Area')"</p>
  
  <p>then I got an ERROR:</p>
  
  <blockquote>
    <p>AssertionError: ForeignKey() is invalid. First parameter to ForeignKey must be either a model, a model name, or the string 'self'</p>
  </blockquote>
  
  <p>please help!</p>