Facebook Container is an extension on Firefox.  Check your extensions under settings to see if you have it.  On my Firefox toolbar it appears as a fence icon. Other than that, I know nothing about it.

Just found the problem.  Facebook Container (fence icon shown in toolbar) hides sites from Facebook to prevent Facebook tracking.  Click on the fence icon and allow FB to track SeekingAlpha.  Now can login.

I don't have ghostery and I can't login.  The login page says it can't login with Facebook.  But I don't login with Facebook.  It simply won't accept my email and pw.

I've tried posting several comments today.  None are posting, although two show up under my profile even though they do not show up in the article where I posted them.