CSS STRUCTURE

CSS STRUCTURE

A CSS comprises of style rules that are interpreted by the browser and then applied to the corresponding elements in your document. A style rule is made of three parts

• Selector: A selector is an HTML tag at which a style will be applied. This could be any tag like <h1> or <table> etc.
• Property: A property is a type of attribute of HTML tag. Put simply, all the HTML attributes are converted into CSS properties. They could be color, border font and many more.
• Value: Values are assigned to properties. For example, color property can have value either red or #F1F1F1.

With the above explaination You can then put CSS Style as −selector { property: value } ul{ color :red; } Here <ul> is a selector and color is a property and given value red is the value of that property

The Type Selectors

• The Universal Selectors:Rather than selecting elements of a specific type, the universal selector quite simply matches the name of any element type −* { color: # 0 0 0 0 0 0 ; }This rule renders the content of every element in our document in black.
• The Descendant Selectors: In a case where you wish to apply a style rule to a particular element only when it lies inside a particular element. As given in the following example, style rule will apply to <i> element only when it lies inside <p> tag.
  

  p i { color: # 0 0 0 0 0 0 ; }

• The Class Selectors: You can define style rules based on the class attribute of the elements. All the elements having that class will be formatted according to the defined rule.
  

  black { color: # 0 0 0 0 0 0 ; }
  

  This rule gives what ever value stated in black to the content of every element with class attribute set to black in the document. You can make it a bit more particular.

  
  h1.black { color: # 0 0 0 0 0 0 ; } This only makes changes to all tags h1 with the class black. You can apply more than one class selectors to given element. Consider the following example −
  <p class = " up down" >

  
  This paragraph will be styled by the classes up and down.
• The ID Selectors: You can define style rules based on the id attribute of the elements. All the elements having that id will be formatted according to the defined rule.

  
  # white{ color: # 0 0 0 0 0 0 ; }

  
  This give the value in white to every element with id attribute set to white in your document. it can be made to be more particular like in style but The true power of id selectors is when they are used as the foundation for descendant selectors,
  For example −
  

  # b l a c k h 2 { color: # 0 0 0 0 0 0 ; }
  

  In this example all level 2 headings will be displayed in black color when those headings will lie with in tags having id attribute set to black.
• The Child Selectors: You have seen the descendant selectors. There is one more type of selector, which is very similar to descendants but have different functionality.
  

  body > p { color: # 0 0 0 0 0 0 ; }
  

  This gives all the paragraphs in black if they are direct child of body element. Other paragraphs put inside other elements like div or td would not have any effect of this rule.
• The Attribute Selectors: styles can only be added to HTML elements with particular attributes. The style rule below will match all the input elements having a type attribute with a value of text −
  

  input[type = "text"] { color: # 0 0 0 0 0 0 ; }
  

  The advantage to this method is that the <input type = "submit" />element is unaffected, and the color applied only to the desired text fields.

Rules of Attribute Selectors

Unlike the other selectors, the attribute selectors has some rules that governs it.

• p[lang]: Selects all paragraph elements with a lang attribute.
• p[lang="fr"]: Selects all paragraph elements whose attribute has a value of exactly "fr".
• [lang~="fr"]: Selects all paragraph elements whose lang attribute contains the word "fr".
• p[lang|="en"]: Selects all paragraph elements whose lang attribute contains values that are exactly "en", or begin with "en-".

Multiple Style Rules

You may need to define multiple style rules for a single element. You can define these rules to combine multiple properties and corresponding values into a single block as defined in the following example

h1 { color: # 3 6 C ; font-weight: normal; letter-spacing: .4em; margin-bottom: 1em; text-transform: lowercase; }

Here all the property and value pairs are separated by a semicolon (;). You can keep them in a single line or multiple lines. For better readability, we keep them in separate lines.

Grouping Selectors

You can apply a style to many selectors if you like. Just separate the selectors with a comma, as given in the following example

h1, h2, h3 { color: # 3 6 C ; font-weight: normal; letter-spacing: .4em; margin-bottom: 1em; text-transform: lowercase; }

This define style rule will be applicable to h1, h2 and h3 element as well. The order of the list is irrelevant. All the elements in the selector will have the corresponding declarations applied to them. You can combine the various id selectors together as shown below −

# c o n t e n t , # f o o t e r , # s u p p l e m e n t { position: absolute; left: 510px; width: 200px; }