anybody can clearly define to me what is pseudo and why we use it?

Answer 1

Let's say you have a class C. This class C is applied to an "a" element (or a "div", or whatever). That element can be is several states. The most commonly used state is the hover state, when the user mouse is above the element. You can style such states, for example you invert the text and background color, or you underline the text for example, This is when "a.C:hover" can be used used in the css. The ":hover" is the pseudo class, which can be combined with the regular css class definition as before..

Look here for more: http://www.w3schools.com/Css/css_pseudo_classes.asp

Answer 2

ohh! thnx a lot.