The search created for a drop-down menu does not work

I am creating a web page with a drop-down menu with different data and to make it easier I want to put a search to put the name you want to search and appear, but it does not work for me.

Could someone help me?

This is the code I am using:

<!-- sidebar -->            
                <div id="sidebar">
                    <div class="inner">

                        <!-- Search -->
                            <section id="search" class="alt">
                                <form method="post" action="#">
                                    <input type="text" name="query" id="query" placeholder="Search" />
                                </form>
                            </section>

                        <!-- Menu -->
                            <nav id="menu">
                                <header class="major">
                                    <h2>SPORTS</h2>
                                </header>
                                <ul>
                                    <li><a href="index.php">SOCCER</a></li>
                                    <li><a href="generic.php">Generic</a></li>
                                    <li><a href="elements.php">Elements</a></li>
                                    <li>

                                        <span class="opener">SOCCER</span>
                                        <span class="opener">EUROPE</span>
                                        <span class="opener">TOP COUNTRIES</span>
                                        <span class="opener">ENGLAND</span>
                                        <ul>
                                            <li><a href="england1/premier-league1.php" target="_blanck">PREMIER LEAGUE</a></li>
                                            <li><a href="england1/championship1.php" target="_blanck">CHAMPIONSHIP</a></li>
                                            <li><a href="england1/league-one1.php" target="_blanck">LEAGUE ONE</a></li>
                                            <li><a href="england1/league-two1.php" target="_blanck">LEAGUE TWO</a></li>
                                            <li><a href="england1/national-league1.php" target="_blanck">NATIONAL LEAGUE</a></li>
                                            <li><a href="england1/football-league-trophy1.php" target="_blanck">FOOTBALL LEAGUE TROPHY</a></li>
                                            <li><a href="#">AMATEUR</a>
                                                <ul>
                                                    <li><a href="england1/isthmian-league1.php" target="_blanck">ISTHMIAN LEAGUE,OR. DIV</a></li>
                                                    <li><a href="england1/national-league-north1.php" target="_blanck">NATIONAL LEAGUE NORTH</a></li>
                                                    <li><a href="england1/national-league-south1.php" target="_blanck">NATIONAL LEAGUE SOUTH</a></li>
                                                    <li><a href="england1/northern-league1.php" target="_blanck">NORTHERN LEAGUE, PR. DIV</a></li>
                                                    <li><a href="england1/premier-league-2-1.php" target="_blanck">PREMIER LEAGUE 2</a></li>
                                                    <li><a href="england1/southern-league1.php" target="_blanck">SOUTHERN LEAGUE, PR. DIV</a></li>
                                                    <li><a href="england1/the-fa-womens-super-league1.php" target="_blanck">THE FA WOMEN'S SUPER LEAGUE</a></li>
                                                </ul>
                                            </li>
                                        </ul>

...

(The other names follow the same lines)