Fixed spelling

Author: weerox

steps/01-01-letters.html

@@ -5,7 +5,7 @@
 ---
 <p>
   You can search words for letters, and/or determine whether they contain a certain letter.
-  Try it yourself. Write the the letter <span class="regex">a</span> into the field below.
+  Try it yourself. Write the letter <span class="regex">a</span> into the field below.
 </p>
 <div class="playfield verbose">
   <input type="text" value="" class="regex" reference="a">