Example URL / webpage where you want to block the slideshow? Typically having Flash set to Never Activate or using a "Flash Control" or "Flash Block" extension will prevent slideshows that are Flash-based. And those that are based upon JavaScript can be blocked with an extension for blocking or limiting JavaScript. https://addons.mozilla.org/en-US/firefox/addon/yesscript/ - ''lets you make a blacklist of sites that aren't allowed to run JavaScript'' https://addons.mozilla.org/en-US/firefox/addon/noscript/ - ''will block all JavaScript - you will need to 'allow' domain-by-domain - a royal pain in the backside for most people''