JSFiddle - React, Tailwind, and code Playground

HTML

<div id="menu"><!-- Aqui el menu -->
                <ul id="menu-horizontal">
                    <li><a href="index.php?b=0">Inicio</a></li>
                    <li><a href="index.php?b=1">Quien somos</a></li>
                    <li><a href="">Proyectos realizados</a>
                    <ul>
                        <li><a href="index.php?b=2">Carteles</a></li>
                        <li><a href="index.php?b=3">Peanas</a></li>
                        <li><a href="index.php?b=4">Iluminaci&oacute;n</a></li>
                        <li><a href="index.php?b=5">Decoraci&oacute;n</a></li>
                        <li><a href="index.php?b=6">Industrial</a></li>
                        <li><a href="index.php?b=7">Cerveza</a></li>
                    </ul>
                    </li>
                    <li><a href="index.php?b=8">Contacto</a></li>
                </ul>
            </div> 
<p>ELEMENTO DEBAJO DEL MENU</p>

CSS

#menu{background:#666;}
#menu-horizontal { background-image: url('./webimages/breadcrumbImage.png'); background-position: -30px -30px; background-repeat:repeat-x; height: 30px; margin:0 auto; }
#menu-horizontal li { width: 180px; text-align:center; list-style:none;   }
#menu-horizontal li:hover { background-image: url('./webimages/breadcrumbImage.png'); background-position: -30px -120px; background-repeat:repeat-x; font-weight:bold; }
#menu-horizontal li a { text-transform:uppercase; font-style:italic; text-decoration:none; text-align: center; line-height: 30px; font-size: 13px; color: white; text-decoration: none;  }

#menu-horizontal li ul li{ float:none;  }

ul#menu-horizontal li { float: left; display: inline; position: relative; }
ul#menu-horizontal li:hover ul{ display: block; }

ul#menu-horizontal ul { display: none; position: absolute; top: 30; left:0; margin:0; padding:0; }
ul#menu-horizontal ul li { display:block !important; font-weight:bold; width: 180px; background-color:#333; }
ul#menu-horizontal ul li:hover { display:block !important; background-image: url('./webimages/breadcrumbImage.png'); background-position: -30px -120px; background-repeat:repeat-x; font-weight:bold; width: 180px;}