text: Title: nbviewer is rendering my ipynb in abnormal way.
  Body: Hello,
  First, thanks for using Jupyter Notebook Viewer (nbviewer).
  I think, I found a bug. Please check the below.
  
  nbviewer is rendering my ipynb(`ch9_note.ipynb`) in abnormal way. 
  Without any description, it will be better to click directly the below link.
  
  https://nbviewer.jupyter.org/github/gritmind/my-review-notes/blob/master/code/book/pymldg/note_ipynb/ch9/ch9_note.ipynb
  
  As you see, the rendering is abnormal. It renders something like in a horizental way.
  
  The below link is just from github with the same ipynb file(`ch9_note.ipynb`).
  
  https://github.com/gritmind/my-review-notes/blob/master/code/book/pymldg/note_ipynb/ch9/ch9_note.ipynb
  
  You can see the rendering is good (but, slow because of not using nbviewer :D). 
  On this account, the ipynb file(`ch9_note.ipynb`) itself is good.
  
  Therefore, I guess, the error is related to nbviewer itself.
  Would you check this bug report? Thanks.
  
  plus...
  
  Interestingly, another file(`ch1_note.ipynb`) is fine. You can see the below link, nbviewer successfully renders it.
  
  https://nbviewer.jupyter.org/github/gritmind/my-review-notes/blob/master/code/book/pymldg/note_ipynb/ch1/ch1_note.ipynb
  
  Is there any difference between `ch1_note.ipynb` and `ch9_note.ipynb` in accordance with nbviewer redering?