how to have 2 classes on one item html code example

Example 1: how to write 2 class in html

<div class="nav nav-centered nav-reversed navbar navigation-block"></div>

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.