add multiple classes to element code example

Example 1: css multiple classes

//HTML Code
<div class = 'firstClass secondClass'></div>

//CSS Code
.firstClass.secondClass {
  
}

Example 2: css assign multiple classes to one element

To specify multiple classes, separate the class names with a space,
e.g. <span class="classA classB">.
This allows you to combine several CSS classes for one HTML element.