Few things destroy user trust faster than a browser displaying "Your connection is not private" when someone tries to visit your website. That red warning screen tells visitors that your site is potentially dangerous, and the vast majority of people will click the back button immediately. They will never return. Understanding SSL certificate errors and how to resolve them is essential for any website owner.
This guide explains the most common SSL errors, what causes each one, and the exact steps to fix them.
What SSL Certificates Actually Do
An SSL certificate creates an encrypted connection between a visitor's browser and your web server. This encryption prevents anyone on the network between the visitor and your server from reading or modifying the data being transmitted. It protects login credentials, payment information, personal data, and even the content of the pages being viewed.
Beyond security, SSL certificates are now a ranking factor for Google search results. Websites without HTTPS enabled rank lower than equivalent sites with valid certificates. Every modern browser also marks HTTP sites as "Not Secure" in the address bar, which further erodes visitor confidence.
Expired Certificate Errors
SSL certificates have expiration dates. When a certificate expires, browsers immediately block access to the site with a warning page. Let's Encrypt certificates expire every 90 days, while certificates from commercial authorities like DigiCert or Comodo typically last one year.
If your certificate expired, the fix depends on your hosting setup. If you use Cloudflare, their edge certificates renew automatically and this error should not occur unless you have a misconfigured origin certificate on your actual server. If you use Let's Encrypt with Certbot, check that the automatic renewal cron job is configured correctly by running a renewal dry run from your terminal.
Domain Name Mismatch Errors
A mismatch error occurs when the domain name in the browser does not match the domain name listed on the SSL certificate. This commonly happens when you access your site using www.yourdomain.com but your certificate only covers yourdomain.com without the www prefix, or vice versa.
The fix is to ensure your certificate covers all variations of your domain. Most certificate providers support Subject Alternative Names that let you list multiple domains on a single certificate. When using Let's Encrypt, include both your root domain and your www subdomain in the certificate request command.
Mixed Content Warnings
Mixed content occurs when your HTTPS page loads some resources like images, scripts, or stylesheets over plain HTTP. Even though the main page is encrypted, loading any resource over HTTP creates a security vulnerability and triggers a browser warning.
To fix mixed content, search your HTML and CSS files for any URLs that begin with http:// and change them to https:// or use protocol relative URLs that begin with //. The most common culprits are hardcoded image references, external font imports, and third party script includes that were copied from old documentation.
Self Signed Certificate Errors
Self signed certificates are certificates that were not issued by a trusted Certificate Authority. Browsers do not trust them because there is no independent third party verifying the identity of the server. While self signed certificates provide encryption, they provide no authentication, which means a visitor has no way to verify they are connecting to your actual server rather than an impersonator.
The fix is simple: replace the self signed certificate with one from a trusted authority. Let's Encrypt provides free certificates that are trusted by all major browsers. There is no legitimate reason to use a self signed certificate on a production website in 2026.
Secure Your Site Without the Headaches
SSL configuration should be invisible to your visitors. They should see a padlock icon in their address bar and never think about it again. If they see a warning instead, you have already lost their trust.
We configure and maintain SSL certificates for businesses that need their websites to always show as secure and trustworthy. Subscribe to Surefire Studios today and never worry about certificate errors again.