Resolution 1:
Add the following URLs into the trusted sites in the Internet options. To do this, follow these steps:
1. Start Internet explorer.
2. Click Tools, click Internet options, Click the Security tab, and then click Trusted Sites. Add the following URLs:
http://*.live.com
http://*.dynamics.com
Resolution 2:
Enable protected Mode in the tools and in the Internet options: To do this, follow these steps:
1. Start Internet explorer.
2. Click Tools, click Internet options, click the Security tab, and then click Trusted Sites. Click to select the Enable Protected Mode check box.
3. Save and close the Internet Explorer window.
You should be now able to login to the CRM Online organization successfully.