You can use this addon: https://addons.mozilla.org/de/firefox/addon/foxreplace/?src=search https://addons.mozilla.org/de/firefox/addon/foxreplace/?src=... Appl

You can use this addon: https://addons.mozilla.org/de/firefox/addon/foxreplace/?src=search https://addons.mozilla.org/de/firefox/addon/foxreplace/?src=... Apply an autoload rule with these settings: Name: zero length replacement HTML: Output only URL: <entering no url matches all sites> Replace: (\uFEFF|\u200B|\u200C) Type: Regular expression With: <span style="background-color:#F00 !important">&#x1f633;</span>