Box model: This is the css very important piece of content, each element as a box, the box model by content (content), padding (padding), margin (margins) and the border (border) which four attributes of. In addition, in the box model, the width and height of the height as well as width the two auxiliary properties.
Property respectively: border, border margin, margins padding, padding, content, content
Floating layout: CSS is Float (floating), the element will move left or right, the elements around it will be re-arranged. Elements after the floating element will be around it. Element before the floating element will not be affected.
If you put several floating elements put together, if there is space, then they will be adjacent to each other.
After the floating elements, the surrounding elements will be rearranged in order to avoid this, clear property, the clear property specifies the element can not appear on both sides of the floating element.