Animating a CSS gradient background on the hover event

Question

I have some menu items that are styled using a background gradient on hover using the following styling:

#sidebar ul          


        

Answer 1

Animation on gradients aren't supported yet. However this site provides a pleasing approach for a animated kind of feel on hover-

http://sapphion.com/2011/10/css3-gradient-transition-with-background-position/

Sample css:-

#DemoGradient{  
    background: -webkit-linear-gradient(#C7D3DC,#5B798E);  
    background: -moz-linear-gradient(#C7D3DC,#5B798E);  
    background: -o-linear-gradient(#C7D3DC,#5B798E);  
    background: linear-gradient(#C7D3DC,#5B798E);  

    -webkit-transition: background 1s ease-out;  
    -moz-transition: background 1s ease-out;  
    -o-transition: background 1s ease-out;  
    transition: background 1s ease-out;  

    background-size:1px 200px;  
    border-radius: 10px;  
    border: 1px solid #839DB0;  
    cursor:pointer;  
    width: 150px;  
    height: 100px;  
}  
#DemoGradient:Hover{  
    background-position:100px;  
} 

Answer 2

Try this as a hack:

<div class="background-animate">
  <div class="content">Hi im content</div>
</div>

And style it

.background-animate {
    position: relative;
    z-index: 10;
    display: block;
    background: transparent;
}
.background-animate:before {
    content: "";
    position: absolute;
    transition: opacity .35s ease-in-out;
   -moz-transition: opacity .35s ease-in-out;
   -webkit-transition: opacity .35s ease-in-out;
    top:0; left: 0; right: 0; bottom: 0; z-index:-1;
    background: -moz-radial-gradient(center, ellipse cover, #ffffff 40%, #e9eae9 100%); /* FF3.6-15 */
    background: -webkit-radial-gradient(center, ellipse cover, #ffffff 40%,#e9eae9 100%); /* Chrome10-25,Safari5.1-6 */
    background: radial-gradient(ellipse at center, #ffffff 40%,#e9eae9 100%); /* W3C, IE10+, FF16+, Chrome26+, Opera12+, Safari7+ */
}
.background-animate:hover:before {
    opacity: 0;
}
.background-animate:after {
    content: ""; opacity: 0;
    transition: opacity .35s ease-in-out;
   -moz-transition: opacity .35s ease-in-out;
   -webkit-transition: opacity .35s ease-in-out;
    position: absolute;
    top:0; left: 0; right: 0; bottom: 0; z-index:-1;
    background: -moz-radial-gradient(center, ellipse cover, #ffffff 80%, #e9eae9 100%); /* FF3.6-15 */
    background: -webkit-radial-gradient(center, ellipse cover, #ffffff 80%,#e9eae9 100%); /* Chrome10-25,Safari5.1-6 */
    background: radial-gradient(ellipse at center, #ffffff 80%,#e9eae9 100%); /* W3C, IE10+, FF16+, Chrome26+, Opera12+, Safari7+ */
}
.background-animate:hover:after {
    opacity: 1;
}

It basically does an opacity switch between to gradients. Demo found here https://codepen.io/anon/pen/eWOEoR

Answer 3

It seems gradients don't support transitions yet (still):

Use CSS3 transitions with gradient backgrounds

If you use a background image rather than a css3 gradient, then you can use css transition to animate it in and out.