As per the navigation issue, on ".rt-block" you have some rules set on it which set padding/margin. That's causing the space of hte navigation. Set them to 0 (the top value anyway) and the space will recede.
As per the slideshow issue, as a default rule you set this
.rt-grid-1, .rt-grid-2, .rt-grid-3, .rt-grid-4, .rt-grid-5, .rt-grid-6, .rt-grid-7, .rt-grid-8, .rt-grid-9, .rt-grid-10, .rt-grid-11, .rt-grid-12
I mean ON that rule you set margins which make the space you were talking about :). You have this rule defined
So on that rule just set the margin to 0 and that space will go away as well :).