[CSS]background image wont resize according to screensize

Im trying to create a page with a background image about 30px wide and 1200px high (its a linear gradient image) which im tiling on x axis. The problem is that the image wont scale…it always remains the same size no matter how big the browser window is. I tried with this CSS code:

    background-attachment: fixed;
    background-repeat: repeat-x;
    height: auto !important;
    position: fixed;

Thanks very much!