A gradient is a smooth transition of two or more colors. This property is a great option CSS3, however, it is currently available only through the background property and the CSS gradient can be used on the elements of defined width and height.
Why use it?
CSS gradients are useful for speeding up your website's load time. You will probably use a fallback picture anyway, but modern browser won't load it, which will speed it up a bit.
Internet Explorer and Gradients
Internet Explorer 9 and older don't support CSS3 gradients. There is gradient filter for Internet Explorer browsers, however, it doesn't support color stops, radial gradients and angles. Therefore, this guide doesn't cover use of this filter and anything related. If you need more information about IE gradient filter, please, check this.