When I open Ebay in Firefox a message appears saying that

"a script has stopped working" and what do I want to do next.

Continue,debug script or close script.

 

This only happens on Ebay.

Does anybody know what this is or how to fix it.

As always, you may need to update to the latest version of Firefox, then disable all Browser Extensions and test the url again.

 

Generally, "a script has stopped working" means your browser has issues interacting with a site javacript helper file (used to provide web 2.0 features and usability for the site). Sometimes a add-on browser extension will cause havoc by tweaking or censoring the script code before the browser interprets it. So disable, or uninstall, the browser extensions and refresh the page / or close and relaunch the browser and try again. 

Firefox has an option to restart with add-ons deactivated in the Help menu.

Worth a try.

 

I don't use Ebay but also have specific cases where sites freeze FF.

It's not bad enough to abandon FF.

When I really need to use such a site I change to Chrome.