Main content

#content {
  float:left;
  width:75%;
  background:#eee;
}
		

The key to this layout is knowing which of the 2 columns will be shortest and to have that column be shortest across all pages of the site.

Here the sidebar column contains less content than the main content column and so will be shorter.

Where the sidebar ends the background of the container shows through. Because we've set container and sidebar to have the same background it appears as though the sidebar continues.

It's important in this layout to set the background color of the longer column. Setting the background color of the shorter column isn't important, but I usually set it anyway.