html - CSS border-bottom 悬停在导航菜单上

Question

我对 border-bottom 属性有疑问。我希望我的 border-bottom 从 li 元素的底部到顶部，高度为 80px。当我尝试使用 border-top 时，它会将我的“header nav ul li a”元素移动到底部 80px。有人有想法吗？

<section class="intro">
    <header>
        <div class="wrapper">
            <nav>
                <ul>
                    <li class="nav_home"><a href="#" onclick="return false;">Home</a></li>
                    <li class="nav_folio"><a href="#" onclick="return false;">Portfolio</a></li>
                    <li class="nav_about"><a href="#" onclick="return false;">About</a></li>
                    <li class="nav_contact"><a href="#" onclick="return false;">Contact</a></li>
                </ul><!-- end nav-menu ul !-->
            </nav>
        </div>
    </header>
</section>

.wrapper {
    width: 1180px;
    margin: 0 auto;
    position: relative;
}

.intro {
    width: 100%;
    height: 100%;
    background: url(../images/banner.jpg) no-repeat;
    background-position: center center;
    -webkit-background-size: cover;
    -moz-background-size: cover;
    -o-background-size: cover;
    background-size: cover;
}

header {
    top: 0;
    position: fixed;
    left: 0;
    right: 0;
    width: 100%;
    height: 80px;
    color: #aaa;
    text-align: center;
    background: transparent;
    border-bottom: 3px solid rgba(72, 191, 114, 1);
    z-index: 99;
}

header nav {
    float: right;
}

header nav ul {
    list-style: none;
    float: left;
}

header nav ul li {
    position: absolute;
    float: left;
    margin-left: 5px;
    width: 120px;
    border-bottom: 0px solid transparent; 
    -webkit-transition: all 0.4s ease-in-out;
    -moz-transition: all 0.4s ease-in-out;
    -ms-transition: all 0.4s ease-in-out;
    -o-transition: all 0.4s ease-in-out;
    transition: all 0.4s ease-in-out;
    height: 80px;
    line-height: 80px;
} 

header nav ul li a {
    font-size: 1.2em;
    text-transform: uppercase;
    text-decoration: none;
    text-align: center;
    color: #fff;
    outline: none;
}

header nav ul li:hover {
    border-bottom: 80px solid #48bf72; 
    cursor: pointer;
}

Answer 1

使用

box-sizing: border-box;

作为列表元素的 CSS 属性(普通 li 和 li:hover)或将其设置为所有 html 元素的全局属性。

希望对你有帮助