You can stop Opera from caching a page by disabling the browser cache. This can be done by accessing the settings menu in the browser, then navigating to the privacy and security section. From there, you can disable the option to cache pages, preventing Opera from storing any cached copies of webpages. By doing this, Opera will be forced to reload the page each time it is visited, ensuring that you are always viewing the most up-to-date version of the webpage.