This has been solved. As pointed by James in the comment, the link that does not work is not a direct link to an image.
I'm learning python through a ipython notebook online. In the ipython notebook, an image from web is displayed using IPython.display.image. I tried it on my laptop and it works. However, when I try to display other images from web, it does not work.
The scripts that work is:
from IPython.display import Image
url = 'http://upload.wikimedia.org/wikipedia/commons/5/56/Kosaciec_szczecinkowaty_Iris_setosa.jpg'
Image(url,width=300, height=300)
The scripts that do not work (but show a broken image without any other outputs) is:
from IPython.display import Image
url='https://en.wikipedia.org/wiki/Iris_setosa#/media/File:Kosaciec_szczecinkowaty_Iris_setosa.jpg'
Image(url,width=300, height=300)
I saw two other related questions but they still do not answer my questions.
How to display an image from web?
Thank you very much!