Clarify chmod command access permissions

download.html.in

@@ -31,13 +31,13 @@
 
 <p>To install it right away for all UNIX users (Linux, OS X, etc.), type:
 <code class="commands">sudo curl @PROGRAM_URL@ -o /usr/local/bin/youtube-dl<br/>
-sudo chmod a+x /usr/local/bin/youtube-dl</code>
+sudo chmod a+rx /usr/local/bin/youtube-dl</code>
 </p>
 
 <p>If you do not have curl, you can alternatively use a recent wget:
 
 <code class="commands">sudo wget @PROGRAM_URL@ -O /usr/local/bin/youtube-dl<br/>
-sudo chmod a+x /usr/local/bin/youtube-dl</code>
+sudo chmod a+rx /usr/local/bin/youtube-dl</code>
 </p>
 
 <p>You can also use pip: