title: how do i set style of element on content page from master page using java script
body: <p>I have a div element with id "dashbmaindivision" on my content page
  and i have  another element on master page which onclick runs a java script function on the master page. the function is to add css style to the div element with id "dashbmaindivision" on my content page but is not working out</p>
  
  <p>the name of my content page is dashboard</p>
  
  <pre><code>&lt;!--this is my java script function my on master page--&gt;
  
  &lt;script type="text/javascript"&gt;
  
  function changNav() {            
  
  document.dashboard.getElementById("dashbmaindivison").style.backgroundColor ="red"
      }
   &lt;/script&gt;
  
  &lt;!--this is my html of my master page--&gt;
  
  &lt;div style="z-index:4"&gt;
       &lt;a href="#" onclick="changNav()" id="openbtn" runat="server" style="font-size:x-large; color:white;" class="place-right"&gt;&lt;span&gt;&amp;times&lt;/span&gt;&lt;/a&gt;
      &lt;/div&gt;
  
   &lt;!--this is my html of my content page--&gt;
  &lt;asp:content id="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"&gt;
  &lt;div  id="dashbmaindivison" runat="server"&gt; &lt;/div&gt;
  &lt;/asp:content&gt;
  </code></pre>
  
  <p>i expect that the style which is the background color of my div element with id "dashbmaindivison" on the content page would change.</p>