Someone asked me how they could execute code when an Atlas page first loaded. In the 'Atlas' xml-script declarative section, add a load attribute to the <application element. The load attribute points to your javascript function. Its that simple.

<%@ Page Language="C#" %>
<html>
<head>
</head>
<body>
    <form ID="Form1" runat="server">
        <atlas:ScriptManager id="Script" runat="server">
        </atlas:ScriptManager>
    </form>
   
    <script type="text/javascript">
    function onLoad(){
        alert("Hello, run your code here!");
    }
    </script>

    <script type="text/xml-script">
        <page xmlns:script="http://schemas.microsoft.com/xml-script/2005">
            <components>
                <application load="onLoad">
                </application>
            </components>
        </page>
    </script>
</body>
</html>