Line below tabsheet

Vaadin 6 / 7 / 8 Framework UI
1

I create a new Vaadin 7 project with eclipse and add following lines to main class.

/**

  • Main UI class
    */
    @SuppressWarnings(“serial”)
    public class AaaaUI extends UI {
    @Override
    protected void init(VaadinRequest request) {
    final VerticalLayout layout = new VerticalLayout();
    layout.setMargin(true);
    setContent(layout);
    final TabSheet tbs = new TabSheet();
    tbs.hideTabs(true);
    tbs.addComponent(new Label(“Test label”));
    //
    layout.addComponent(new Label(“outer label 1”));
    layout.addComponent(tbs);
    layout.addComponent(new Label(“outer label 2”));
    }
    }

The tabsheet component displays a bottom gray line. I could not find its css definition. Is there a way to hide this margin below the tabsheet.

Thanks
Yasin