title: Changing visibility of a button
body: <p>I have the following button on every page:</p>
  
  <pre><code>  &lt;a href="#"  class="mainMenu sideBarButton orange" style="visibility:hidden" id="myButton"&gt;Start&lt;/a&gt;
  </code></pre>
  
  <p>and a popup form which has the following button</p>
  
  <pre><code>   &lt;input type="button" value="Log in" onClick="assignValue()";/&gt;
  </code></pre>
  
  <p>clicking this calls:
          function assignValue(){
                sessionStorage.setItem("booleanLoggedIn", true);
        }</p>
  
  <p>And I'm hoping that the value associated with key "<code>booleanLoggedIn</code>" is true for the whole session, so that:</p>
  
  <pre><code>window.onload = function(){
      var loggedIn = sessionStorage.getItem('booleanLoggedIn');
       if (loggedIn){  
       document.getElementById('myButton').style.visibility="visible";
  
      }
  </code></pre>
  
  <p>means that as long as the user is logged in, the button "<code>Start</code>" will appear on the page?</p>
  
  <p>But this is not working correctly, and I have no idea why. I know that the value "<code>true</code>" is getting stored correctly..</p>