Togli il background-color di qui:
#container-leftmenu-left, #container-rightmenu-right, #container-3columns-right, #container-3columns-left { float: left; width: 100%;}
template.css riga 592
e di qui:
#container-leftmenu-content, #container-rightmenu-content, #container-3columns-content, #container-1columns1 { float: left; width: 100%;}
template.css riga 574