In CSS, How to show a div tag as a block when clicked and normal when clicked again?

How to show a “div” tag as a block when it’s content is clicked and show normal, when clicked again?
Can someone please show me how to do this using CSS?

a div’s normal display style is block, so what do you mean by “normal”.

unless css3 has an onclick psuedo class the only other way I can think of is to use javascript to attach an onclick event handler to the div to change its display style when clicked.