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CSS - @ Rules
  • 时间：2024-12-22

CSS - @ Rules

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This chapter will cover the following important @ rules −

    The @import: rule imports another style sheet into the current style sheet.

    The @charset rule indicates the character set the style sheet uses.

    The @font-face rule is used to exhaustively describe a font face for use in a document.

    The !important rule indicates that a user-defined rule should take precedence over the author s style sheets.

NOTE − There are other @ rules which we will cover in subsequent chapters.

The @import rule

The @import rule allows you to import styles from another style sheet. It should appear right at the start of the style sheet before any of the rules, and its value is a URL.

It can be written in one of the two following ways −

<style type = "text/css">
   <!--
      @import "mystyle.css";
      or
      @import url("mystyle.css");
      .......other CSS rules .....
   -->
</style>

The significance of the @import rule is that it allows you to develop your style sheets with a modular approach. You can create various style sheets and then include them wherever you need them.

The @charset Rule

If you are writing your document using a character set other than ASCII or ISO-8859-1 you might want to set the @charset rule at the top of your style sheet to indicate what character set the style sheet is written in.

The @charset rule must be written right at the beginning of the style sheet without even a space before it. The value is held in quotes and should be one of the standard character-sets. For example −

<style type = "text/css">
   <!--
      @charset "iso-8859-1"
      .......other CSS rules .....
   -->
</style>

The @font-face Rule

The @font-face rule is used to exhaustively describe a font face for use in a document. @font-face may also be used to define the location of a font for download, although this may run into implementation-specific pmits.

In general, @font-face is extremely comppcated, and its use is not recommended for any except those who are expert in font metrics.

Here is an example −

<style type = "text/css">
   <!--
      @font-face {
         font-family: "Scarborough Light";
         src: url("http://www.font.site/s/scarbo-lt");
      }
      @font-face {
         font-family: Santiago;
         src: local ("Santiago"),
         url("http://www.font.site/s/santiago.tt")
         format("truetype");
         unicode-range: U+??,U+100-220;
         font-size: all;
         font-family: sans-serif;
      }
   -->
</style>

The !important Rule

Cascading Style Sheets cascade. It means that the styles are appped in the same order as they are read by the browser. The first style is appped and then the second and so on.

The !important rule provides a way to make your CSS cascade. It also includes the rules that are to be appped always. A rule having a !important property will always be appped, no matter where that rule appears in the CSS document.

For example, in the following style sheet, the paragraph text will be black, even though the first style property appped is red:

<style type = "text/css">
   <!--
      p { color: #ff0000; }
      p { color: #000000; }
   -->
</style>

So, if you wanted to make sure that a property always appped, you would add the !important property to the tag. So, to make the paragraph text always red, you should write it as follows −

<html>
   <head>
      <style type = "text/css">
         p { color: #ff0000 !important; }
         p { color: #000000; }
      </style>
   </head>

   <body>
      <p>Tutorialspoint.com</p>
   </body>
</html>

Here you have made p { color: #ff0000 !important; } mandatory, now this rule will always apply even you have defined another rule p { color: #000000; }

It will produce the following result −