How to 'measure up' bg-images in CSS

Lets say I want to give image parameters in HTML, I would do something like this:

<img src="/pics/background.gif" width="4" height="77">

But now I'm trying to do this with CSS, then I would think I have to do something like this:

body {
background-image: url("/pics/background.gif") ;
background-repeat: repeat;
background-attachment: fixed;
width : 4;
height : 77;
}

But that doesn't seem to work for me, when looking at my page in Opera I see a mistake in how the browser 'looks' at my picture. That's why I want to give the exact parameters.

Hope someone has a nice tip

Alex