Hey Alexander--in order to make the message about sandboxed iframes not being supported only show up in older versions of IE, I think it needs to work a little differently. For content that you do want to show in old versions of IE but not in newer browsers, you put the entire thing in a comment so that modern browsers ignore it but IE picks it up. (Also, it looks like for the base64 case it was written as just lt IE 9, not lte.)
Didn't I do the opposite? There was one spot where we had "if lt IE 9" before and I ought to have changed it so that we have "if lte IE 9" in both places.
Hey Alexander--in order to make the message about sandboxed iframes not being supported only show up in older versions of IE, I think it needs to work a little differently. For content that you do want to show in old versions of IE but not in newer browsers, you put the entire thing in a comment so that modern browsers ignore it but IE picks it up. (Also, it looks like for the base64 case it was written as just lt IE 9, not lte.)
Hope you can take a look at this tomorrow!