# apply-css ## What it does This extension includes: * a background script, "background.js" * a page action It adds the page action to every tab the user opens. Clicking the page action for a tab applies some CSS using [tabs.insertCSS](https://developer.mozilla.org/docs/Mozilla/Add-ons/WebExtensions/API/tabs/insertCSS). Clicking again removes the CSS using [tabs.removeCSS](https://developer.mozilla.org/docs/Mozilla/Add-ons/WebExtensions/API/tabs/removeCSS). ## What it shows * some basic page action functions * how to apply and remove CSS.