If you are having problems with Internet Explorer 9, try to go to your settings and reset them to their default values.

This is done by going to "tools" then "options" then "advanced"

There you will see "Reset Internet Explorer settings" with a button that reads "Reset".

Press the button and see if it resolves your issue. The issues people are having are related to new or changed security settings within IE9. IE9 is perfectly compatible with this website, only specific security settings may be interfering. This is also a good procedure as some "new" default security setting may increase your browser security overall.

Additionally you can add this site "co-ar15.com" to your trusted sites list, this will allow any content to bypass specific security settings. It should only be used on sites that are safe and preferably SSL secured (ie: https://) prefix.