What should I do with the add-on prompts I am getting in Internet Explorer 9?

When browsing you will occasionally see messages on a Notification bar at the top of the screen about add-ons.

Add-ons provide extra features to Internet Explorer (IE) and you are usually prompted to give permission to install them, although they can install in the background and as part of other programmes. It is up to you whether you allow add-ons. They will be required for some websites, but you should be aware that they will slow down the performance of IE.

More info about the Notification bar and managing add-ons is available from Microsoft.