…o the author of the picture (which is always nice to do) and adds more credibility to your article. Especially when using images from websites that are not free image providers, it is really important to link back to where you got the content, as you could get in trouble if you don’t. You’d be surprised how easy it is to commit copyright infringement.
Sorry, but this is a bit misleading. It is never okay to just grab an image from a website. Even if you link to the source, grabbing an image without permission is copyright infringement. I’ve seen too many businesses get in trouble for this, so we always need to use appropriate sources or ask permission. You’d be surprised how many folks are thrilled to have you use their image when you ask permission. (Screenshots by example are a different story, and it depends on the purpose of your writing.)