将星号添加到bootstrap 3中的必填字段？

我的HTML有一个被调用的类.required,它被分配给必需的字段.这是html:

    
    

       Username
       

         
       
    
    
E-mail

    
Password

    
Password (again)

    
first name

    
last name

    
 
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我把以下内容添加到了我的CSS中;

.form-group .required .control-label:after {
  content:"*";color:red;
}

仍然不会*在必填字段周围产生红色.我在这里想念的是什么？在引导程序3中没有直接引入*必需字段的方法.

编辑:*在条款和条件中没有立即出现在checkbox.how来解决这个问题？

.form-group.required没有空间使用.

.form-group.required .control-label:after {
  content:"*";
  color:red;
}

编辑:

.form-group.required:not(.checkbox) .control-label:after, 
.form-group.required .text:after { /* change .text in whatever class of the text after the checkbox has */
   content:"*";
   color:red;
}

    
   

      

          
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好的第三次编辑:

CSS回到原来的样子

.form-group.required .control-label:after { 
   content:"*";
   color:red;
}

HTML:

     
   

      

          
             I have read and agree to the Terms of Service
         
      
   

假设这就是HTML的样子

   E-mail
   

要在标签右侧显示星号:

.form-group.required .control-label:after { 
    color: #d00;
    content: "*";
    position: absolute;
    margin-left: 8px;
    top:7px;
}

或者在标签的左侧:

.form-group.required .control-label:before{
   color: red;
   content: "*";
   position: absolute;
   margin-left: -15px;
}

要制作漂亮的大红色星号,您可以添加以下行:

font-family: 'Glyphicons Halflings';
font-weight: normal;
font-size: 14px;

或者,如果您使用Font Awesome添加这些行(并更改内容行):

font-family: 'FontAwesome';
font-weight: normal;
font-size: 14px;
content: "\f069";

.form-group .required .control-label:after应该是.form-group.required .control-label:after.删除.form-group和.required之间的空格是一种变化.