fix typo

Author: nicoder

property/background-image/index.html

@@ -104,7 +104,7 @@ <h2 class="property-name">
         </p>
         <div class="example-description">
           <p>You can specify an <strong>angle</strong>, either in <strong>degrees</strong>, or with keywords.</p>
-<p>When using degress, you specify the <em>direction</em> of the gradient, or when it ends. So <code>0deg</code> means the the <strong>top</strong> of the element, like 12:00 on a clock.</p>
+<p>When using degrees, you specify the <em>direction</em> of the gradient, or when it ends. So <code>0deg</code> means the the <strong>top</strong> of the element, like 12:00 on a clock.</p>
 <p>In this example, <code>45deg</code> means 2:30, or the top right corner.</p>
 
         </div>