CSS Border in Layouts

Vaadin 6 / 7 / 8 Framework UI
1

Hello,
Having a bit of trouble getting CSS borders to show with Vaadin (7) layouts.
Basically, I’ve got a HorizontalLayout that gets added to a VerticalLayout in the UI like this:

public class MyView extends VerticalLayout implements View
{
	public MyView()
	{
		super();
		setSizeFull();
		setStyleName("admin-view");
		setMargin(false);

		HorizontalLayout header = new HorizontalLayout();
		header.setSizeUndefined();
		header.setWidth("100%");
		header.setSpacing(true);
		header.addStyleName("bottomborder");

		addComponent(header);
			.
			.
			.
	}
}

The salient CSS entry looks like this:

[code]
.bottomborder {
border-bottom: 4px solid #353637;
}

[/code]FireBug shows the style is applied to various

elements, but no border is shown.

[code]

[/code]I’ve tried many other combinations, but to no avail.
Any useful insights would be much appreciated.
Thanks,
Peter