I would suggest to disable border for highlighted widgets because it brakes layout of the page. Instead we can use
#dm_page.edit .dm_widget .dm_widget_inner {
outline: 2px groove #D3D3D3;
border: none;
/* border-radius: 0 4px 4px 4px;
-moz-border-radius: 0 4px 4px 4px;
-webkit-border-radius: 0 4px 4px 4px;*/
}
outline does not change box model.