[SOLVED] How Can I Override Image Background?

I'm trying to set the background of an img to white and added some custom CSS code in the Atahualpa CSS code area. But it doesn't work. Can someone tell me how to fix this?

This is what CSS that <img> is using when I use Firebug in FireFox.

.post img {
background-color: #F3F3F3;
border: 1px solid #DDDDDD;
border-radius: 3px 3px 3px 3px;
padding: 5px;
}

Here is my CSS code in my theme to override the background color:

img.indeed post.img {
background-color: #FFFFFF;
border: 0 solid #DDDDDD;
border-radius: 3px 3px 3px 3px;
padding: 5px;
}

Here is the code in my post:

<img class="indeed" align='right' border='0' src='http://www.indeed.com/images/myimage.gif' width="116" height="23">