I am receiving an unsecure/untrusted website message. What is causing this? What should I do to resolve this?

Fidelity Charitable has updated the digital certificate we use to increase the level of security for our website. Browsers on older operating systems may not be compatible with this upgraded certificate. The updated digital certificate is made by Entrust, a certificate provider that Fidelity Charitable uses for secure communications. Entrust is one of the industry standards. This issue is best resolved by downloading the newest version of Entrust Root Certificate Authority and adding this trusted security provider to your computer. To do this, please follow these steps:
1. Go to https://www.entrust.com/get-support/ssl-certificate-support/root-certificate-downloads/
2. Midway down the page, click on "Download" from the section "Entrust Root Certificate Authority—G2"
3. Close all browser windows and then restart the browser