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fallback property

Supplying a CSS fallback property is a common technique to ensure cross-browser compatibility. In the example below, the first background-image specifies an image file, which all browsers are able to render. The additional ones after that specify the more recent linear-gradient() function, which all browsers may not support. The browser uses those values only if it is able to interpret them, otherwise reverting to the image file value as a fallback.

div {
    background-image: url(img/gradient.png);
    background-image: -webkit-linear-gradient(to bottom, #dddddd, #aaaaaa);
    background-image: -moz-linear-gradient(to bottom, #dddddd, #aaaaaa);
    background-image: linear-gradient(to bottom, #dddddd, #aaaaaa);

Note here that you can use this fallback technique to apply a mix of standardized or vendor-prefixed properties, whichever works.