There is no such thing as a background tag in HTML. What might have been called a background tag in older versions of HTML — the background attribute of the <BODY> HTML tag — was used to display a background image for a web page. The current recommendation from the World Wide Web Consortium (W3C) is HTML 4.01/XHTML 1.0. In this recommendation, the background attribute is deprecated: It is no longer considered valid HTML. The related <BODY> attribute bgcolor, which could be considered a background tag, is also deprecated.
Cascading Style Sheets (CSS) should be used to set all background effects in a valid HTML or XHTML web page. Using CSS to define background properties is much more flexible than the older method. The background attribute, or background tag, was limited to displaying a background image. Background properties in CSS can define where the background image starts, how it repeats, and whether it scrolls with the rest of the page or stays in the same place. CSS background properties can be applied to an entire web page or elements on the page.
Background properties include background-color, background-image, background-attachment, background-position, and background-repeat. All of those properties can be consolidated under the background property instead of being set as separate properties. This is called a shorthand property.
Like the old bgcolor attribute, background-color can be in the form of an RGB value, a hex code, or a color name. The background of any element this property is applied to will display in that color. The value for background-image is the URL of the image.
The other properties — background-attachment, background-position, and background-repeat — can be defined, but if they are not, the default values will be used. Background-repeat is used to repeat the background either vertically or horizontally; by default, it repeats vertically and horizontally. Background-attachment makes the background image either scroll with the rest of the page, which is the default, or stay in one place. The background-position default is the upper left-hand corner of the element.
Different web browsers may display the background properties differently, or require more specific definitions in the CSS. For example, even though Internet Explorer® 8 supports the inherit value for some properties, it does not support it for background properties. In Firefox®, the background-position property does not work properly if the background-attachment property is not set to fixed. Developers should test their pages in a variety of browsers to make sure the pages display as intended.