CSS3 gradients let you display smooth transitions between two or more specified colors.
Earlier, you had to use images for these effects. However, by using CSS3 gradients you can reduce download time and bandwidth usage. In addition, elements with gradients look better when zoomed, because the gradient is generated by the browser.
Types of gradients are :
For more: http://www.w3schools.com/css/css3_gradients.asp