The Content panel in Firefox OptionsPreferences includes settings related to how a website's content is displayed. This article explains what settings are available.
Firefox lets you choose which websites are allowed to send you notifications. To learn more, see the article Web Push notifications in Firefox. Click Choose… to make changes to the list of allowed sites.
Default font and Size: Web pages are usually displayed in the font and size specified here (measured in pixels). However, web pages can override these choices unless you specify otherwise in the Fonts dialog. Click the Advanced… button to access the Fonts dialog and to change this and other fonts optionspreferences.
You can also set the minimum web page font size. This is useful to prevent sites from using overly small fonts that are barely readable.
Text and Background: Here you can change the default text and background color to be used on web pages that haven't specified that information. Click on the color samples to select colors.
Link Colors: Here you can change the default colors for Web links. Click on the color samples to select colors.
Some web pages are offered in more than one language. Click the Choose… button to specify your preferred language or languages.
Languages Dialog: To add a language, click Select a language to add…, choose the language, and click the Add button. Remove a language by selecting it in the list of active languages and clicking the Remove button. You can also reorder languages using the Move Up and Move Down buttons to determine the most preferred one in case a page is provided in multiple languages.