JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="nav">
				<li>
					<a href="#" title="">Главная</a>
				</li>
				<li class="dropdown">
                    <div><a href="#" title="">Новости</a></div>   
					<ul>
						<li><a href="#">Все</a></li>
						<li><a href="#">Просшествия</a></li>
						<li><a href="#">Экономика</a></li>
						<li><a href="#">Общество</a></li>
					</ul>                     
				</li>
				<li>
					<a href="#" title="">Погода</a>					
				</li>
				<li>
					<a href="#" title="">Программа</a>					
				</li>
				<li>
					<a href="#" title="">Афиша</a>
				</li>
			</ul>

CSS

body {
    background: gray;
}
.dropdown div {
    position: relative;
    border: 1px solid transparent;
}
.dropdown div a {
    position: relative;
	display: block;
	text-decoration: none;
	color: #0076d1;
	padding: 10px;
    z-index: 4;
}
.dropdown div:before {
    display: block;
    content: "";
    position: absolute;
    border: 1px solid transparent; 
    margin-left: -1px;    
    margin-top: -1px;
    padding: 1px;
    height: 39px;
    width: 100%;
    left:-1px; top: -1px;
    z-index: 3;
    background: linear-gradient(0, yellow, white);  
    /*Фикс проблеым с градиентом и полоской при наличии прозрачной границы*/
    background-size: 100% 112.5%;
    background-position: 0 -0.063em;
}
.dropdown:hover div:before {
    border: 1px solid #d0d0d0;
    border-bottom: 1px solid transparent;
}

#nav {
	position: relative;
	list-style: none;
}
#nav  li {
	float: left;
	border: 1px solid transparent;
}
#nav  > li:hover {
	border: 1px solid #d0d0d0;
}
#nav > li > a {
	display: block;
	text-decoration: none;
	color: #0076d1;
	padding: 10px;
}
#nav  > li:hover > a{
	color: #000;
}
#nav li ul {

background: linear-gradient(yellow, white);
    z-index: -1;
	list-style: none;
	position: absolute;
	top: 39px;
	border: 1px solid #fff;
	padding: 0;
	margin-left: -1px;
    margin-top: 3px;
	display: none;
	opacity: 0;
}
#nav li ul li a {
	display: block;
	text-decoration: none;
	color: #868686;
	padding: 10px;
}
#nav li ul li a:hover {
	text-decoration: underline;
}
#nav li:hover ul { 
	border: 1px solid #d0d0d0;
	display: block;
	opacity: 1;
}
#nav .dropdown:hover {
	border-bottom: none;
}