CSS selector

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#CSS selector is divided into two types

Id and Class Selectors

#If you want to set CSS styles in HTML elements, you need to set the "id" and "class" selectors in the element.

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#id selector

The id selector can specify a specific style for HTML elements marked with a specific id.

The HTML element uses the id attribute to set the id selector, and the id selector in CSS is defined with "#".

The following style rules apply to the element attribute id="para1":

      
  
php中文网(php.cn)
 
这一段不受css样式影响。
  

Run the program to try it

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The ID attribute should not start with a number. IDs starting with numbers do not work in Mozilla/Firefox browsers.

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class selector

class selector is used to describe the style of a group of elements. The class selector is different from the id selector. , class can be used in multiple elements.

The class selector is represented by the class attribute in HTML. In CSS, the class selector is displayed with a dot ".":

In the following example, all objects with the center class HTML elements are all centered.

Example

      
  
标题居中
 
段落居中。
  

Run the program to try it

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You can also specify specific HTML elements using classes.

In the following example, all p elements use class="center" to center the text of the element:

Example

      
  
这个标题将不会受到影响
 
这一段将居中对齐
  

Run the program and try it

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The first character of the class name cannot use numbers! It won't work in Mozilla or Firefox.