Em HTML pressione Ctrl + F e procure por:
.main-inner .column-center-outer {
E logo abaixo cole:
-webkit-border-bottom-left-radius: 20px;
-moz-border-radius-bottomleft: 20px;
border-bottom-left-radius: 20px;
Depois procure por:
.main-inner .fauxcolumn-right-outer .fauxcolumn-inner {
-webkit-border-bottom-right-radius: 20px;
-moz-border-radius-bottomright: 20px;
border-bottom-right-radius: 20px;
Visualize . se tiver tudo certinho Salve .