These are called gradients and you can use them like this:
#main {
background: #ea9d27; /* Old browsers */
background: -moz-linear-gradient(top, #ea9d27 0%, #ffffff 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#ea9d27), color-stop(100%,#ffffff)); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, #ea9d27 0%,#ffffff 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, #ea9d27 0%,#ffffff 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #ea9d27 0%,#ffffff 100%); /* IE10+ */
background: linear-gradient(to bottom, #ea9d27 0%,#ffffff 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ea9d27', endColorstr='#ffffff',GradientType=0 ); /* IE6-9 */
}
#content article { background: #ea9d27; /* Old browsers */
background: -moz-linear-gradient(top, #ea9d27 0%, #ffffff 100%); /* FF3.6+ */
background: -webkit-gradient(linear, left top, left bottom, color-stop(0%,#ea9d27), color-stop(100%,#ffffff)); /* Chrome,Safari4+ */
background: -webkit-linear-gradient(top, #ea9d27 0%,#ffffff 100%); /* Chrome10+,Safari5.1+ */
background: -o-linear-gradient(top, #ea9d27 0%,#ffffff 100%); /* Opera 11.10+ */
background: -ms-linear-gradient(top, #ea9d27 0%,#ffffff 100%); /* IE10+ */
background: linear-gradient(to bottom, #ea9d27 0%,#ffffff 100%); /* W3C */
filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ea9d27', endColorstr='#ffffff',GradientType=0 ); /* IE6-9 */
}
For this example I used the exact same color you provided on your image. If you want to play around to get different gradients you can use this handy tool.
First part of above mentioned code will change background for website itself and second part will change background for content area, so you can use two separate gradients.