Avoid Divitis, Classitis, Tagitis, etc.

<div class="header">Our Solar System</div>

or even

<div class="header"><h1>Our Solar System</h1></div>

<h1>Our Solar System</h1>

<div class="basketball">
            <ul>
              <li>Mark Few</li>
              <li>Roy Williams</li>
              <li>John Calipari</li>
              ...
            

<ul class="basketball">
              <li>Mark Few</li>
              <li>Roy Williams</li>
              <li>John Calipari</li>
              ...