html - Set styles per div -

I am new to CSS and not a programmer, I understand what a class is and I think what is a div But what I have not been able to know is to divide styles.

Any help appreciated,

Joost Verplancke

< P> In your HTML

  & lt; Div class = "MyClass" & gt; see me! & Lt; / Div & gt;  

In your CSS

  .myclass {background-color: # aaa; }   
  Edit   
 As told by Dave, you can provide multiple classes for one element. This means that you can essentially make modular styles  
 for example, in your HTML  
   
 
 In your CSS 
 
  .myclass {background-color: # aaa; Color: # 1dd; }. MyColor {color: # 111; }  
 
 You should also note that the order attribute in the class attribute has conflicting settings in different styles. That is,  class = "myClass myColor"  is exactly the same as  class = "mycolor myClass" . Which contradictory setting is actually used in CSS. 
 
 This means, instead of forming  myClass  from  color  in the above example,  colors  to  myColor , you have to change your CSS to switch around it 
 
  .mycolor {color: # 111; }. MyClass {background-color: #by; Color: # 1dd; }