Centering an image within a div

Applying text-align: center to your banner div will center its inline and inline-block children (which encompasses the img tag).

The reason why your code wasn't working is because margin: 0 auto will only center block elements.

Try setting the image’s display property to block:

banner {
    height: 100px;
    width: 960px;
    padding-bottom: 10px;
}

banner img {
    border: none;
    display: block;
    margin: 0 auto;
}