Watch this video to learn how to write CSS.

But basically, we write CSS like this..

name { property: value; }

For example: This will make ALL Paragraphs 14px in size.

p { font-size: 14px; }

We write a Class like this: This will make all elements with the Class of .class blue in colour

.class { color: blue; }

We write an ID like this: This will make any element with the ID of #id red in colour

#id { color: red; }

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Sometimes we will see a CSS like this..

div { margin: 25px 10px 25px 10px; }

Do not panic, this is the same as..

div { 
margin-top: 25px;
margin-right: 10px;
margin-bottom: 25px;
margin-left: 10px;
 }

This is called CSS Shortcuts. Read more about it here.