Steve,
That's a normal warning and there's nothing that can be done to prevent it. Basically, Javascript from one domain (Facebook) is trying to access and alter content from another domain (your site). There's a warning thrown in the Javascript console because that behavior isn't allowed as it could introduce security issues.
Facebook (and every other social network that has social widgets.. like buttons, share buttons, etc) tries that method because on some browsers it does work. If it doesn't, then they have to fall back to other options to update their Like counter and other features that you're displaying on your site.
In general though, even though that message is shown in the console log, you shouldn't see any negative issues on your site and most users never use the error console and won't see it either. If you feel there are actual functional issues though, just let us know, and we'll gladly investigate further.
Thanks,
Alex