There is some sort of left margin or padding on the slider. It does not line up with the elements below it. When you start to make the page smaller, you can really see this margin I'm talking about.
Anyhow, try this: Change your CSS to
#page .pad {
padding: 40px;
background-color: transparent;
}
This produced a much cleaner result for me, not sure if it's exactly what you want though. Being that you're using BS2, you may have to write some media queries to handle your extra styles.