This is why it's best to host the image yourself. Rather it's by uploading it to your own server or using sites like:
http://postimage.org/
or
http://tinypic.com/

This way, you have control.
Question: Based on the code, it looks like it is a screenshot. Is this one of your screenshots or one of Microsoft's? If it's from your profile, then did you remove or edit the name of this file? If it's MS's then the issue may be because they updated the file or simply removed it.
The funny thing about browsers is that they hold a temporary internet cache for images and info. If you or Shadow can still see image, while others can't, then this is why. Clearing your cache or temporary files should fix this. I deal with this all the time when I'm working on websites.