CSS Layouts - Pro CSS Techniques - page 149

Managing Floats
Earlier in this chapter we mentioned that one of the problems with floating blocks of content
in CSS is that the parent container collapses down behind the floated content, as shown in
Figure 7-25. What you probably wanted was an effect more like that shown in Figure 7-26.
Figure 7-25. Collapsed float
Figure 7-26. Cleared float
There are a few ways of dealing with this issue. Earlier we suggested adding some CSS to
the footer div (a footer with no content):
#footer {
clear:both;
}