In Post Ad Not Displaying.

I just set up in the post ad plugin here: http://www.railroad.net/amtrak-train-derails-in-nebraska-193.html

It seems to be displaying ads correctly in chrome but not in IE or Firefox.

The plugin settings are set to "Do Not Show Title" and "Strip Default Style."

The same issue occurs when both of those settings are unchecked as well.

The ad code is showing up in source but isn't displaying on the site.

Any help is much appreciated.

Thanks in advance!