Where do you see this message box?

Can you post a link to a publicly accessible page (i.e. no authentication or signing on required)?

In some cases we have seen this happen if the website tries to open HTML content via an EMBED tag. This doesn't work in Firefox.

website is www.overthetopchristmaslights.com. it is a muic file to be played when visited to website. worked fine until a few days ago. i had same prob once before and i loaded a plugin. works fine in IE.

That is about playing an MP3 file via an 'embed' tag.

<embed src="http://www.overthetopchristmaslights.com/Music/BillyGorilly_JingleBells.mp3" autostart="true" hidden="true">

I don't know what plugin Firefox would use in your case. I think that this would normally be the QuickTime plugin and not the Windows Media Player plugin.

Do you see the .mp3 file extension listed with either of those plugins if you check that on the about:plugins page?

You can open "about:" pages via the location/address bar.

• "about:" is a protocol to access special pages

No do not see mp3 on either but have both plugins loaded. I am really getting disgusted with firefox. I can no longer use my vault and now having probs with sound. with they would quit doing updates.

You can use this bookmarklet to convert the EMBED tag to an AUDIO tag and use the built-in HTML5 media player.

• https://en.wikipedia.org/wiki/Bookmarklet

javascript:(function(){var cE='audio',eE=document.querySelectorAll('object,embed');for(i=0;E=eE[i];i++){N=document.createElement(cE);N.setAttribute('src',E.src||E.data);N.setAttribute('controls','');N.setAttribute('autoplay','true');E.parentNode.replaceChild(N,E)}})()