How to style a block element?

Question

css

There is a table, these blocks are in the table. How to apply styles to block elements. Or ask separately?
a.rollover {
background: url(...);
display:block;
width: 64px
height: 64px;
}
a.rollover:hover {
background-position: 0 -64px;
}

Answer 1

Our group is a block element, the color changes on hover. How to align this picture?