Remove the center
. Then it should work.
Also make sure you have it for all browsers:
background-image: -webkit-linear-gradient(top, rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0) 75%, rgba(255, 255, 255, 0.95) 100%);
background-image: -moz-linear-gradient(top, rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0) 75%, rgba(255, 255, 255, 0.95) 100%);
background-image: -o-linear-gradient(top, rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0) 75%, rgba(255, 255, 255, 0.95) 100%);
background-image: -ms-linear-gradient(top, rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0) 75%, rgba(255, 255, 255, 0.95) 100%);
background-image: linear-gradient(top, rgba(255, 255, 255, 0) 0%, rgba(255, 255, 255, 0) 75%, rgba(255, 255, 255, 0.95) 100%);