What is the default value of width and height of <div> element?
Does it depends on browsers?
If so, how to calculate them?
If by itself and outside another block level element an empty and unstyled <div> has no width or height. If an empty <div> is within another block level element it will act like a paragraph break so it has "height" there. In other words, it will give you a line-height break when empty (<div></div>) and unstyled. You can change all this with CSS.