Make sure Yammer (https://www.yammer.com) and your Microsoft Dynamics CRM Online URL are in the same security zone in Internet Explorer.
Internet Explorer 8: You can view the security zone for the current site in the bottom status bar of the browser.
Internet Explorer 9 and 10: You can click the File menu and then click Properties to view the Zone information.
Note: If the Menu Bar is not enabled in Internet Explorer 9 or 10, you will need to enable it to see the File menu. Simply right-click the top of the browser window and then click to enable the Menu Bar if it is not already selected.
Verify that the Zone info for both the Microsoft Dynamics CRM Online website and Yammer are the same. If both sites are not in the same zone, you need to manually add the URL to the same zone. To add both URLs to the Trusted Sites zone, complete these steps:
1. Click the Tools menu in Internet Explorer and then click Internet Options.
2. Click the Security tab and then click Trusted Sites.
3. Click the Sites button.
4. Add your Microsoft Dynamics CRM Online URL and then click Add.
5. Add the Yammer URL (https://www.yammer.com) and then click Add.
6. Click Close and then click OK.