Scroll bar moved layout slightly to left

Question

If content on ALL of my site either did or didn't require a scroll bar, the transitions when clicking from page to page would all look smooth. Unfortunately I have some pages that are short (and so the browser displays no display bar) and other pages that are long, and when the scroll bar appears, my content gets moved slightly to the left.   I suppose I could just keep adding a bunch of new paragraphs at the bottom of my short pages until a scroll bar appears, but this problem is bugging me. I'd like to fix it the real way. To visualize this problem see attached pictures below.
And here's some of the code that I think is relevant to my issue here.
body {
    background-attachment: fixed;
    background-image: url(images2/palisades.jpg);
    background-repeat: no-repeat;
    background-color: #000000;
    background-position: center left;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
    margin: 0;
    padding: 0;
.header {
    width: 1000px;
    margin-left: auto;
    margin-right: auto;
    height: 50px;
Below: the scroll bar pushes content slightly to the left.

Answer 1

Actually, this one looks pretty simple.
The first page shown is long enough to need a vertical scrollbar. When that scroll bar kicks on, the actual width of the page changes slightly, so the content (which appears to be centered) will shift to the left when the scroll bar appears.
If it really bothers you (most visitors would never notice it) you can add a scroll bar to every page on your site (the pages that don't need it will pop up with a grayed out bar that doesn't allow scrolling) and your pages won't shift anymore if you add in overflow-y:scroll to the body tag css....
body {
     overflow-y:scroll;