fix typo in css - buttons

docs/_includes/css/buttons.html

@@ -88,7 +88,7 @@
 
 
   <h2 id="buttons-active">Active state</h2>
-  <p>Buttons will appear pressed (with a darker background, darker border, and inset shadow) when active. For <code>&lt;button&gt;</code> elements, this is done via <code>:active</code>. For <code>&lt;a&gt;</code> elements, it's done with <code>.active</code>. However, you may use <code>.active</code> on <code>&lt;button&gt;</code>s should you need to replicate the active state progammatically.</p>
+  <p>Buttons will appear pressed (with a darker background, darker border, and inset shadow) when active. For <code>&lt;button&gt;</code> elements, this is done via <code>:active</code>. For <code>&lt;a&gt;</code> elements, it's done with <code>.active</code>. However, you may use <code>.active</code> on <code>&lt;button&gt;</code>s should you need to replicate the active state programmatically.</p>
 
   <h3>Button element</h3>
   <p>No need to add <code>:active</code> as it's a pseudo-class, but if you need to force the same appearance, go ahead and add <code>.active</code>.</p>