You create a website for a client and make sure to secure usage rights for all the images used. The photographer of the header image is only willing to allow use for 2 years. Considering the lifespan of a typical website, that seems reasonable. You inform the client of the terms of all the licensing agreements when you hand over the site as complete. Two years and six months later, you get an angry email from the photographer – the client has not removed the photo or renewed the license and they’re demanding payment.
