Wicket WebMarkupContainer

In Wicket, the WebMarkupContainer is being used quite often. One small thing about the visibility when using it.
When you need to make the initial state invisible and then later on visible (via ajax), the component would not be visible unless its setOutputMarkupPlaceholderTag is true.

Container.setVisible(false);
Container.setOutputMarkupPlaceholderTag(true);
add(Container);

This is due to the fact that components when setVisible(false) do not get any tags in output markup at all in wicket.
The dev team's interesting discussion is here.