There are some mail services that require you to go to a website to verify yourself as a sender. However, I'm not sure why you are having difficulties with that because in Firefox, JavaScript is enabled by default.

Could you copy/paste the error you're getting, or provide a screen shot of it? This article has tips on capturing screenshots: How do I create a screenshot of my problem? Please cut out or blur any sensitive information in the image before attaching it to your reply.

Also, your Firefox identified itself to the forum as version 28. Is that correct?

Version 28 is not secure; Mozilla discloses security flaws after each new release. Is something holding you back from upgrading to Firefox 47? Please let us know so we can suggest solutions or workarounds.

To roll back the user interface changes in Firefox 29 and later, you might be interested in this extension: https://addons.mozilla.org/firefox/addon/classicthemerestorer/