CSS Syntax

A CSS rule set contains a selector and a declaration block.

p{
  color: #333333;
}  

Explanation:-
Above whole block is known as Declaration Blog. Here, p is selector, color is property and #333333 is value to this property.
  • Selector: Selector indicates the HTML element you want to style. It could be any tag like <p>,<h1>, <title> etc.
  • Declaration Block: The declaration block can contain one or more declarations separated by a semicolon.
  • Property: A Property is a type of attribute of HTML element. It could be color, border etc.
  • Value: Values are assigned to CSS properties. In the above example, value “#333333” is assigned to color property.

Case Sensitivity in CSS

CSS property names and many values are not case-sensitive. Whereas, CSS selectors are usually case-sensitive, for instance, the class selector .headerblock is not the same as . headerBlock.

Therefore, to be on safer side, you should assume that all components of CSS rules are case-sensitive.