uCertify CIW – Advanced HTML5 & CSS3 Specialist Practice Test

The key idea is how CSS links to a background image using a URL inside the background-image (or shorthand background) property. In the sample CSS, the URL points to a file named background.gif, so that image is the one applied as the background. The other file names refer to different images or formats, which would only be used if the CSS were pointing to them instead. The GIF extension simply tells us the image format of the referenced file, but what matters here is that the CSS rule references background.gif exactly, making it the background image in that sample.