If your content inside #childRightCol and #childRightCol are floated left or right, just add this into css:
#childRightCol:before { display: table; content: " "; }
#childRightCol:after { display: table; content: " "; clear: both; }
#childLeftCol:before { display: table; content: " "; }
#childLeftCol:after { display: table; content: " "; clear: both; }