Introduction

After taking the step to enhance website security by installing an SSL certificate, one might anticipate the 'padlock' icon to immediately indicate a secure connection. However, this isn't always the case. Many website owners face an unexpected error: "Loading mixed (insecure) display content". This article delves into what this error means and how to resolve it.

What is Mixed Content

Mixed content refers to scenarios where an HTTPS web page includes resources, like images, scripts, or styles, loaded over an insecure HTTP connection. When this occurs, even though the initial site is loaded securely over HTTPS, some resources are not encrypted, thereby making the connection partially secure. This weakens the security of the entire page.

There are two types of mixed content:

Display Content: Such as images, videos, or audio. This type won't necessarily block users from accessing the site but will show a warning.
Active Content: This includes scripts, stylesheets, and iframes. Loading such resources over HTTP can seriously compromise the security of your site.

Why is Mixed Content a Concern

Security Risks: Attackers can manipulate non-secure content, even if the page itself is loaded over HTTPS. This can lead to man-in-the-middle attacks.
Trust Issues: Web browsers will flag the site as "Not Secure". This can discourage users from staying on or returning to the site.
Site Functionality: Browsers may block mixed content, affecting the site's usability.

How to Identify Mixed Content on Your Website

Browser Indicators: Most browsers will show a warning icon, usually a padlock with a warning or an exclamation mark.
Browser Developer Tools: By inspecting your website using browser developer tools, you can locate the exact resources causing the mixed content error.

Steps to Resolve Mixed Content Errors:

Update to HTTPS: Review your website's code and update every instance of "http://" to "https://". This is especially necessary for internal resources.
Relative URLs: Use protocol-relative URLs (//domain.com/resource). However, this method has some drawbacks and it's recommended to explicitly use "https://".
Content Delivery Network: Ensure your CDN supports HTTPS and update resource links accordingly.
Check CMS & Database: For database-driven sites or those using a CMS, ensure links stored in the backend are updated to HTTPS.
Server-side Redirection: Implement server-side solutions, like rules in your .htaccess file (for Apache servers), to enforce HTTPS loading.
Update Third-party Content: Ensure any plugins, widgets, or third-party integrations are HTTPS-compatible.

Preventive Measures for the Future:

Always Use HTTPS for New Resources: When adding new resources, always ensure they're loaded over HTTPS.
Set Content Security Policy (CSP): A CSP can help in detecting and mitigating certain types of attacks, including mixed content.

Conclusion

Securing a website is not just about installing an SSL certificate but ensuring that all elements of the site maintain that security. Addressing mixed content is an essential step towards creating a truly secure and trustworthy website for your visitors.