what do you mean by hover boxes? hover boxes (divs, scrollboxes, blogs, whatever) are just boxes that look a certain way until you mouse over them, and then they can change in any way you define them. a common way is to adjust the opacity (how 'see-through' it is -- opacity:.90;) so that the box is 'dark' when your mouse is elsewhere, but when you mouseover it lights up and becomes more visible.
beginning if you've done css before, you've definitely used hover codes in links. say you want a link to be normal with no borders or backgrounds, but when you mouseover to click on it, it has a one black underline on the bottom. that would look like this:
a:link, a:active, a:visited denote what the link looks like when it's 'normal' or has been clicked on before. a:hover denotes what the link will look like when you mouseover it. to give it an underline, you can see it has the extra element border-bottom:1px solid #000;.
in scrollboxes the same concept applies to scrollboxes. just like links, you can set divs to be one way when you're not mousing over them, and another when you are.
say you want a normal div to have a white border, and when you mouseover it, the border becomes black:
just like in all css, you're free to play around with all these attributes for the desired effect.