3-13的示例中有一段這樣的代碼

<div?class="form-group?has-success">

為什么在bootstrap的css文件中沒有找到這樣的一個類名設置，跟has-success有關的類名只有下面這幾類

has-success .help-block,

Line 2814: .has-success .control-label,

Line 2815: .has-success .radio,

Line 2816: .has-success .checkbox,

Line 2817: .has-success .radio-inline,

Line 2818: .has-success .checkbox-inline,

Line 2819: .has-success.radio label,

Line 2820: .has-success.checkbox label,

Line 2821: .has-success.radio-inline label,

Line 2822: .has-success.checkbox-inline label {

Line 2825: .has-success .form-control {

Line 2830: .has-success .form-control:focus {

Line 2835: .has-success .input-group-addon {

Line 2840: .has-success .form-control-feedback {