You can paste CSS into this lightweight editor (Ace) and then generate a userChrome.css file for download. All text entry and file generation is done within the page without sending any code to my server. This page is not backed up as you work. The editor may object to some CSS selectors and properties not used on the web. That's normal.

/* Replace this SAMPLE CONTENT with your own CSS */ /* No blue swipe on tabs when loaded */ .tabbrowser-tab .tab-loading-burst { display: none !important; }