Top header gradient help

Greetings.

My blog is at http://www.hollisadoption.com.

I want to make the black at the top gradiate into the green. I made a gradient strip and uploaded it and modified this part of my style.css:

body {
padding: 0 0 2em 0;
margin: 0;
text-align: center;
font: 62.5% verdana, sans-serif;
background: #008000 url(images/top2.gif) repeat-x;
color: #333;
line-height: 150%;
}

Where top2.gif was the name of my 10 x 210 pixel gradient strip.

What happened was it gradiated from balck to green down the length of the whole page and not just the 200 or so pixels at the top.

Help? If that makes sense?