We don't set a background color on any of the pages here.
Many people think a white background makes a page more readable.
However, if we set the background color to white in the HTML of each page it would override the default or local settings for some browsers. We prefer to leave the color unspecified, so that you can individually choose the default color that you prefer via your browser's configuration. With other browsers there are usually similar ways to change the default colors with one of the browser's configuration files or menus.