Default theme: adding border to sidebar

Having a hard time trying to find where in the CSS I can add a border to the left of the sidebar. What I tried was was to use a backgroud image that included a rule but I can’t figure out where to put the code. I tried putting it in this section of the style.css file:

/* Begin Sidebar */
#sidebar
{
padding: 20px 0 10px 0;
margin-left: 545px;
width: 190px;
}

but the background image ended up being indented with a bit of the light blue background color of the sidebar showing to the left. So I assume I’m either inserting it in the wrong area or am doing it wrong.

Here’s the code I used:

/* Begin Sidebar */
#sidebar
{
background-image: url(images/blog_bckgrnnd.jpg);
background-repeat: repeat-y;
padding: 20px 0 10px 0;
margin-left: 545px;
width: 190px;
}

If someone can set me straight on this it would be greatly appreciated.

Thanks.

Fred