If we keep .container and #page-header in the same div, the div gets a bottom border from #page-header and {left-padding:15px, right-padding: 15px }  from bs3 .container. Since borders doen't consider padding, it seem to be projecting 15px left and right from the rest of the contents.

![header-container-not_in_same_div](https://f.cloud.github.com/assets/1054350/1030320/16036b9e-0eb2-11e3-9f40-ebfc1619d858.png)