css code help please

[England]

how can i code this right to centre the image and to stop the image been repeated

.altbg {
    background: #000000 url(http://www.moddedwarfare2.com/forum/-images-/SniperRifle.png) repeat-x top left; 
    height: 70px;
    width: 100%;
    vertical-align: text-bottom;
    border: 1px solid #434647;
}

thankyou in advance