When adding an image to your page on iblog.stjschool.org with a link to an image on another site, you may get unexpected results. This is called hotlinking: when images appear to be embedded on your page, but are simply linked to someone else's page.
Advantages: no bandwidth or disk quota used from your account because you are not storing/delivering the image here.
Disadvantage: many "smart" sites forbid and display a 404 error. Some may just limit to a finite number, say 5 visits per day.