id selector is introduced using "#", which has the same effect as the "." of the class selector. Example: #div{} Let's do a specific experiment: html:

      
  
勇气
 
三年级时，我还是一个胆小如鼠的小女孩，上课从来不敢回答老师提出的问题，生怕回答错了老师会批评我。就一直没有这个勇气来回答老师提出的问题。学校举办的活动我也没勇气参加。
 
到了三年级下学期时，我们班上了一节公开课，老师提出了一个很简单的问题，班里很多同学都举手了，甚至成绩比我差很多的，也举手了，还说着："我来，我来。"我环顾了四周，就我没有举手。
  

css:

#stress{ color:red; }

Rendering:

In many ways, ID selectors are similar to class selectors, but There are also some important differences:

1. Set id="ID name" for the label instead of class="class name".

2. The ID selector is preceded by a pound sign (#) instead of an English dot (.).