[css] Aligning two divs side-by-side

It's also possible to to do this without the wrapper - div#main. You can center the #page-wrap using the margin: 0 auto; method and then use the left:-n; method to position the #sidebar and adding the width of #page-wrap.

body { background: black; }
#sidebar    {
    position: absolute;
    left: 50%;
    width: 200px;
    height: 400px;
    background: red;
    margin-left: -230px;
    }

#page-wrap  {
    width: 60px;
    background: #fff;
    height: 400px;
    margin: 0 auto;
    }

However, the sidebar would disappear beyond the browser viewport if the window was smaller than the content.

Nick's second answer is best though, because it's also more maintainable as you don't have to adjust #sidebar if you want to resize #page-wrap.