Mozilla Firefox Release 31.0 and how the jquery ui position method calculates the geometry of the bounding box

Mozilla Firefox Release 31.0 and how the jquery ui position method calculates the geometry of the bounding box

I was wondering how the jquery ui position method calculates the geometry of the bounding box  for the following html5.
 
def output_text_field(name,fields,size=50):
    print '<input type="text" name="%s" size="%d" value="%s">' % \
          (name,size,fields.get(name,''))
 
I noticed some difference in the behavior of
 
$('#_test_academic_advisor_name).position( off:'#_academic_advisor_name', my: 'left top', at:'right center')
 
 
between Mozilla Firefox Version 31.0, which is the current release', and Mozilla Firefox Version 22.0.  Is it possible that the  jquery ui position method calculates the geometry of the bounding box  for the following html5.
 
def output_text_field(name,fields,size=50):
    print '<input type="text" name="%s" size="%d" value="%s">' % \
          (name,size,fields.get(name,''))
 
differently between Mozilla Firefox Version 31.0, which is the current release', and Mozilla Firefox Version 22.0?
Or is the difference in behavior caused by  some other geometry calculation?
 
Thank you very much.
          Frank