css gradient background button

Well, they used this in default state:

background: #0079FF;
background: -webkit-gradient(linear, 0% 0%, 0% 100%, from(#0096FF), to(#005DFF));
background: -webkit-linear-gradient(0% 0%, 0% 100%, from(#0096FF), to(#005DFF));
background: -moz-linear-gradient(center top, #0096FF, #005DFF);

For hover they have other colors of course. Just change the color for your needs.