What is a copyright?
A photograph, painting, sculpture, music and written word, anything we create digital or physical is automatically protected under copyright law. Photos you find online even if they do not have a copyright notice are not yours and you may not reproduce them without permission.
Permission or license
Obtaining permission or license is difficult because the website where you find the photo may not be the company that has ownership of the photo. At the least you could be facing a request to remove the photo. At worst you could end up in legal and financial trouble. Make sure you have written permission or a creative commons license before you use any photograph on your website or in print.
Sources for Images
Always obtain your images from a reputable source. There are many stock houses that offer low cost royalty free images. Make sure you check the licensing even from these sources. In some cases they are restricted to editorial use. This is especially true of images that have brand name goods in them. licence for web use may not include print use and print license may be restricted to certain types of uses. A good stock house will be most helpful in answering your questions.
Here is a great article on the subject from 12 most.com
Postscript: The 12most.com site seems to be offline permanently. We’ll try to provide another resource in the future. jm 7-21-17