Office 365 SharePoint Online - This website wants to run the following add-on: 'Not Available' from 'Control name is not available'. If you trust the website and the add-on and want to allow it to run, click here

You might get a warning in IE8 when trying to add a new solution in your SharePoint Online site.
IE message -

This website wants to run the following add-on: 'Not Available' from 'Control name is not available'. If you trust the website and the add-on and want to allow it to run, click here...



The warning message is from Internet Explorer (IE) and concerns trusting a custom template file and the SharePoint Online tenant it is stored in.
If you have a Professionals Small Business subscription, to resolve the trust issue and configure your computer for SharePoint Online you will need to add some additional trusted sites as listed below:

1.Open Internet Explorer Tools and select Internet options

2.Select the Security tab -> Trusted Sites -> and verify that Enable Protected mode is unchecked

3.Select Sites and verify that Require server verification (https:) for all sites in the zone is unchecked

4.Under Add this website to the zone -> Add

5.Add the following websites to the zone:

http://*.microsoft.com, http://PutYourDomainHere.microsoft.com and http://*.sharepoint.com