The "m" in that YouTube address indicates the mobile site. Can you find a menu button toward the upper right of the page (stack of 3 dots or 3 horizontal bars) with a "Desktop" item to switch the view? If so, does that fix it?

You also might try: When you have a problem with one particular site that previously worked normally, a good "first thing to try" is clearing your Firefox cache and deleting your saved cookies for the site.

(1) Clear Firefox's Cache

See: How to clear the Firefox cache

If you have a large hard drive, this might take a few minutes. If you do not see the number going down on the page, you can reload it using Ctrl+r to check progress.

(2) Remove the site's cookies (save any pending work first). While viewing a page on the site, try either:

• right-click (on Mac Ctrl+click) a blank area of the page and choose View Page Info > Security > "View Cookies"
• (menu bar) Tools > Page Info > Security > "View Cookies"
• click the padlock or "i" icon in the address bar, then the ">" button, then More Information, and finally the "View Cookies" button

In the dialog that opens, the current site should be pre-filled in the search box at the top of the dialog so you can remove that site's cookies individually.

Then try reloading the page. Does that help?

Thanks. I cleared out the cookies for YT and that did the trick. Now why couldn't the idiots at MF Facebook resolve this quickly and professionally, as you did. I appreciate your kindness. Frank

Do you mean the Firefox page on Facebook? As a platform, FB isn't good for detailed tech support -- formatting is limited and everything gets all mushed together -- so they generally will point you over here if it takes more than a couple sentences and/or a link to an article to resolve an issue.

thanks again for your kindness. frank