Out there in internet land, there is a widely held belief that images found using Google’s image search function are ‘public domain’ and free to use. This is wrong, and thinking otherwise could be costly.
Finding a photo or diagram on Google does not mean that you can freely use that image in a Word document or Powerpoint slide, on a webpage or on your blog, nor anywhere else. The same goes for any other image, piece of writing or piece of music, for that matter.
You wouldn’t steal a shirt from a clothing store just because you can pick it up and try it on. Re-using anything you find on the web just because you can copy and paste it is no different. At the very least you should be aware of your right to copy that content before you do.