Your browser displays a red padlock. The address bar shows “Not Secure.” A warning page appears before your site loads and tells visitors there may be a problem. This is an SSL certificate error, and if it is appearing on your own website, it needs to be addressed the same day you discover it.
SSL errors are usually fixable, but they are not cosmetic. They signal a problem with encryption, domain coverage, or certificate trust, and the longer they remain visible, the more traffic and confidence the site can lose.
What an SSL Certificate Actually Does
SSL stands for Secure Sockets Layer, though the current version of the technology is technically called TLS (Transport Layer Security). The name SSL has stuck in common use, so you will hear both.
When someone visits your website, data travels between their browser and your web server. Without an SSL certificate, that data travels as plain text. Anyone positioned between the visitor and your server, whether on the same public WiFi network or elsewhere in the connection path, could potentially read that data. This includes form submissions, login credentials, and any other information your visitors type into your site.
An SSL certificate enables encrypted communication between the browser and the server. It also confirms that the server delivering your website is actually associated with your domain. This is why the padlock appears in the address bar: it signals that the connection is encrypted and the identity of the server has been verified by a trusted authority.
At this point, a valid SSL certificate is a basic expectation for a business website. Google has used HTTPS (the protocol enabled by SSL) as a ranking signal since 2014. Browsers began labeling non-secure sites more aggressively starting around 2017. Today, a site without a valid certificate displays security warnings in every major browser.
What Causes SSL Certificate Errors
Not all SSL certificate errors are the same. Here are the most common causes.
Expired Certificate
SSL certificates are issued for a specific period of time, typically one or two years, though shorter terms are increasingly common. When the certificate expires, the browser can no longer confirm the connection is secure, and it displays a warning.
Expiration is the most common cause of SSL errors on established sites. It happens when the renewal process is not automated or when the renewal reminder emails are missed (they often go to whoever set up the certificate originally, which may not be you).
Certificate Not Covering the Correct Domain
A certificate is issued for a specific domain or set of domains. If your site is accessible at both `example.com` and `www.example.com`, the certificate needs to cover both. If it only covers one version, visitors who arrive via the other will see an error. Similarly, if you recently migrated to a new domain, the old certificate does not cover the new one.
Certificate Installed on the Wrong Server
When a site is moved to a new hosting server, the SSL certificate needs to be reissued or transferred to the new server. If the migration was done without addressing the certificate, visitors may see errors after the move.
Certificate from an Untrusted Authority
Browsers maintain a list of certificate authorities they trust. Certificates issued by authorities not on that list will trigger warnings. Legitimate certificates from providers like Let’s Encrypt, DigiCert, or Sectigo are trusted by all major browsers. A self-signed certificate (generated without a recognized authority) will trigger a warning in every browser.
Mixed Content
Sometimes the certificate itself is valid, but certain elements on your pages, such as images, scripts, or embedded content, are still being loaded over an unencrypted HTTP connection rather than HTTPS. This is called mixed content. Some browsers will block these elements, and in some cases the browser may display a warning even though the certificate is technically valid.
Why You Cannot Ignore It
Visitors Leave
When a browser displays a certificate warning, many visitors will not proceed. The language browsers use is intentionally alarming. “Your connection is not private.” “Attackers may be trying to steal your information.” These warnings are designed to stop people before they enter any personal data. Your site may be perfectly safe in all other respects, but the warning overrides that.
It Affects Search Rankings
Google treats HTTPS as a positive ranking signal. More directly, if Google’s crawlers encounter certificate errors when trying to access your site, it can affect how your pages are indexed. A persistent certificate error is not a minor inconvenience.
It Damages Credibility
A client, prospect, or vendor who visits your site and sees a security warning may form an impression about how your business operates. This is not fair, but it is real. Certificate errors are visible signs of neglect to anyone who understands what they mean.
Form Submissions and Logins Are at Risk
If your site has contact forms, a login area, or any kind of e-commerce checkout, an expired or invalid certificate means those transactions may not be encrypted. This is a direct risk to anyone who submits information through your site.
What Resolution Usually Looks Like
Step 1: Confirm the Error
The first useful check is a fresh browser session, often incognito mode or a different browser entirely. That rules out a cached certificate locally. If the warning appears there too, visitors are likely seeing the same thing.
Step 2: Identify Who Manages Your Certificate
An SSL certificate is typically managed by the web host. In the hosting control panel (cPanel, Plesk, or the host’s custom dashboard), the SSL or Certificates section often shows the expiration date and status directly.
When the host is unclear, the technical contact information in the domain registrar account often helps identify where the site is actually hosted.
Step 3: Contact Your Hosting Provider
Once you have confirmed the issue, contact your hosting provider’s support. Tell them:
- Your domain name
- What you see in the browser (expired certificate, “Not Secure” warning, specific error message if shown)
- That you need the SSL certificate renewed or reissued
Some hosting providers can renew or reissue a certificate quickly, especially when automation was already in place. Many hosts now offer free certificates through Let’s Encrypt that can be reissued automatically. If your certificate was previously set to auto-renew and renewal failed, the support team can diagnose why and reset it. If DNS, migration, or domain-mismatch issues are involved, the fix can take longer.
Step 4: Verify After the Fix
After the host confirms renewal or reinstallation, a fresh browser check should show the padlock again and the warning should disappear.
If the warning persists, the cause is often a secondary issue such as mixed content or a domain mismatch that support still needs to investigate.
Preventing It from Happening Again
The strongest prevention is usually automated renewal that is confirmed inside the hosting account or maintenance process. Most hosts that use Let’s Encrypt handle renewal automatically, but the automation can still fail if billing lapses, DNS records change, or hosting configuration changes.
If a web support provider is involved, certificate expiration is usually part of routine maintenance. When ownership of that task is unclear, missed renewals become much more likely.
A certificate error is not a catastrophe, and it is usually fixable once the underlying certificate, DNS, or hosting issue is identified. The risk is in leaving it unaddressed and letting visitors encounter warnings while you are unaware. Checking your site in a browser every few weeks, even briefly, is one of the simplest ways to catch problems like this before they affect your business.
Related reading: What to Do When Your Website Goes Down, Website Hosting Explained: What Each Plan Actually Covers, and What Actually Happens During a Website Migration.