>I have Firefox 20.0.1. It says it is the latest version. One .aspx page is generating this error:
>
>"TypeError: this._containers is undefined @ resource://gre/modules/devtools/MarkupView.jsm:331"
>
>I am not using any file like that. So, I assume this is an internal file of Firefox.
>
>Firefox site reports that this is in regards to JQuery. I am not using that. So, I assume Firefox is using it internally. I am unable to find any other information as to know what is causing this.

Do you get the same (or similar) error in other browsers? Did you try to examine this page with developer tools?