Comparing Date Spans

I need to write a query that would compare 2 pairs of dates.A start and end date for both rows. The second start date needs to be >= to the first end date. That is, there should be no gaps between the second start date and first end date.

ex: Good Scenario

First Start: 10/01/2006 First End: 12/31/2007
Second Start: 11/30/2007 Second End: 01/31/2008

ex: Bad Scenario

First Start: 10/01/2006 First End: 12/31/2007
Second Start: 02/01/2008 Second End: 04/30/2008