Undefined index: action : <p>The highlighted line is line 24</p>

<p>Notice: Undefined index: action in C:\xampp\htdocs\authors.php on line 24</p>

<pre><code>  **if($_GET['action'] == "list") {**
        $current = "members";
        $list = "members";
    }
    else if($_GET["list"] == "authors") $current = "authors";
    else $current = "members";
</code></pre>
