CSS is easy to use.

1 define a style that starts with "." And starts?

A global variable starting with ".", such as. Input, is a CSS class. Class = "input" can be referenced so far wherever you want to use this style ";

A local variable starting with "#", for example, # divmain, which is defined for the control named ID. <Div id = "divmain"> </div>

According to the ID, you can define it layer by layer. for example, # nav Li ul a: hover {} This style defines the hover style of all the labels in UL under Li under Nav, that is, the style put with the mouse