What do you do when Certificate Error appears on your web pop up?

When a Certificate Error appears on your web pop-up, first check the URL to ensure it's correct and secure (it should start with "https://"). You can try refreshing the page or clearing your browser's cache. If the error persists, avoid entering any sensitive information and consider accessing the site from a different browser or device. If you trust the site, you can click on "Advanced" and proceed, but be aware of potential security risks.