Round Corner Box
The break-down of the round corner DIV is illustrated:
There are some key notes when I explore this piece of code:
1. The background of an element can be positioned, by which you can control exactly that element's background;
2. An empty element with background is usually used to make up a block's appearance;
3. Float is an extremely useful attribute for positioning the element, and then build the layout;
4. In HTML environment, you always have to break up your overall layout into visual elements, and place them into different HTML wrapper.