Hi byphoto, your Firefox identified itself as Firefox 78. Are you running:

• old release of Firefox 78
• Extended Support Release of Firefox 78
• Firefox 80 with privacy.resistFingerprinting turned on

Your picture shows the eBay site. If Yahoo has turned into eBay, that's definitely a weird problem!

However, if you meant eBay all along, there is a known issue with the "Strict" level of Enhanced Tracking Protection breaking the layout. You can click the purplish shield icon at the left end of the address bar and turn off ETP for the site as a workaround. More info on this feature: Enhanced Tracking Protection in Firefox for desktop.

Thank you so much jscher2000 :)))

Note that the OP is on Mac OS X 10.11

Firefox 79 and newer releases require Mac OS X 10.12 or newer. Users on Mac OS X 10.9 and 10.10 and 10.11 have been moved to the Firefox 78.x ESR version.

• https://support.mozilla.org/en-US/kb/how-download-and-install-firefox-mac
• https://support.mozilla.org/en-US/kb/macos-users-esr

Thank you cor-el :))