You can have more than one class for controls by separating them with space
inside class attribute. But you cann't have more than one class attribute to any controls..
Ex: 1). Two classes
<div class="myclass1 mycalss2">content</div>
2). N number of classes
<div class="myclass1 myclass2 myclass3 ... ">content</div>
Note: If you written repeating style in both the classes they may get overwrite by each other.. So avoid repeating same styles.