Selenium can be used to take screenshots of a web page in order to check for unanticipated changes. This can be done by comparing the captured screenshot with the current screen pixel-by-pixel or by storing the screenshots away and having a human review them. Selenium provides a `save_screenshot` command that can be used to capture screenshots, which can be implemented using plain vanilla webdriver or extensions provided by partner companies like Applitools. The code for taking a screenshot in Ruby and Python is provided as an example and can be found on GitHub for further use and modification.