如何修改我當前的HTML/CSS代碼，以便一旦選擇了一個標簽，底部邊框將被刪除？
這是它目前的樣子:
這是期望的結果:
代碼如下:
<!DOCTYPE html>
<html>
<head>
<title>JavaScript tabs example</title>
<style type="text/css">
ul#tabs { list-style-type: none; margin: 30px 0 0 0; padding: 0 0 0.3em 0; }
ul#tabs li { display: inline; }
ul#tabs li a { color: #42454a; background-color: #dedbde; border: 1px solid #c9c3ba; border-bottom: none; padding: 0.3em; text-decoration: none; }
ul#tabs li a:hover { background-color: #f1f0ee; }
ul#tabs li a.selected { color: #000; background-color: #fff; font-weight: bold; }
div.tabContent { border: 1px solid #c9c3ba; padding: 0.5em; background-color: #fff; }
div.tabContent.hide { display: none; }
#file_content {
width: 100%;
border: 1px solid red;
}
#file_content td {
padding: 5px;
}
</style>
<script type="text/javascript">
var tabLinks = new Array();
var contentDivs = new Array();
function init() {
// Grab the tab links and content divs from the page
var tabListItems = document.getElementById('tabs').childNodes;
for ( var i = 0; i < tabListItems.length; i++ ) {
if ( tabListItems[i].nodeName == "LI" ) {
var tabLink = getFirstChildWithTagName( tabListItems[i], 'A' );
var id = getHash( tabLink.getAttribute('href') );
tabLinks[id] = tabLink;
contentDivs[id] = document.getElementById( id );
}
}
// Assign onclick events to the tab links, and
// highlight the first tab
var i = 0;
for ( var id in tabLinks ) {
tabLinks[id].onclick = showTab;
tabLinks[id].onfocus = function() { this.blur() };
if ( i == 0 ) tabLinks[id].className = 'selected';
i++;
}
// Hide all content divs except the first
var i = 0;
for ( var id in contentDivs ) {
if ( i != 0 ) contentDivs[id].className = 'tabContent hide';
i++;
}
}
function showTab() {
var selectedId = getHash( this.getAttribute('href') );
// Highlight the selected tab, and dim all others.
// Also show the selected content div, and hide all others.
for ( var id in contentDivs ) {
if ( id == selectedId ) {
tabLinks[id].className = 'selected';
contentDivs[id].className = 'tabContent';
} else {
tabLinks[id].className = '';
contentDivs[id].className = 'tabContent hide';
}
}
// Stop the browser following the link
return false;
}
function getFirstChildWithTagName( element, tagName ) {
for ( var i = 0; i < element.childNodes.length; i++ ) {
if ( element.childNodes[i].nodeName == tagName ) return element.childNodes[i];
}
}
function getHash( url ) {
var hashPos = url.lastIndexOf ( '#' );
return url.substring( hashPos + 1 );
}
window.onload = function() {
init()
}
</script>
</head>
<body>
<table id="file_content" cellspacing="0" cellpadding="0">
<tr><td>File Content</td></tr>
<tr>
<td>
<ul id="tabs">
<li><a href="#about">About JavaScript tabs</a></li>
<li><a href="#advantages">Advantages of tabs</a></li>
<li><a href="#usage">Using tabs</a></li>
</ul>
<div class="tabContent" id="about">
<h2>About JavaScript tabs</h2>
<div>
<p>JavaScript tabs partition your Web page content into tabbed sections. Only one section at a time is visible.</p>
<p>The code is written in such a way that the page degrades gracefully in browsers that don't support JavaScript or CSS.</p>
</div>
</div>
<div class="tabContent" id="advantages">
<h2>Advantages of tabs</h2>
<div>
<p>JavaScript tabs are great if your Web page contains a large amount of content.</p>
<p>They're also good for things like multi-step Web forms.</p>
</div>
</div>
<div class="tabContent" id="usage">
<h2>Using tabs</h2>
<div>
<p>Click a tab to view the tab's content. Using tabs couldn't be easier!</p>
</div>
</div>
</td>
</tr>
<tr>
<td></td>
</tr>
</table>
</body>
</html>
將所有選項卡設置為position:relative和top:1px。這將使它們都向下移動1px。給它們一個z-index:-1，這將使它們出現在靜態內容下。將活動選項卡設置為z-index:1或大于0的值。這確保它在頂部，并覆蓋頂部的灰色邊界。
ul#tabs li a {
position:relative;
top:-1;
z-index:-1;
}
ul#tabs li a.selected {
z-index:1;
}工作小提琴
您可以向選定的選項卡添加底部邊框，以覆蓋灰色線條，如下所示:
ul#tabs li a.selected {
color: #000;
background-color: #fff;
font-weight: bold;
border-bottom: 2px solid #fff;
}工作演示。
在你文件的第11行
ul#tabs li a.selected { color: #000; background-color: #fff; font-weight: bold; border-bottom: #fff 2px solid;}解決這個問題的有效方法是將邊界定義為內部邊界。這可以通過使用嵌入的方框陰影來實現。那么就不需要定義負的邊距或相對偏移量來覆蓋邊界，因為它是內部邊界。
header {
box-shadow: inset 0 -1px grey;
background: linear-gradient(whitesmoke, lightgrey);
padding: 0.25em 1em 0 1em;
}
header h1 {
font-size: 1.25em;
}
header > menu.tabs {
display: flex;
gap: 1em;
padding: 0;
margin: 0;
list-style-type: none;
}
header > menu.tabs > li > a {
border: 1px solid transparent;
border-radius: 0.25em 0.25em 0 0;
border-bottom: none;
display: block;
padding: 0.25em 1em;
text-decoration: none;
color: black;
}
header > menu.tabs > li:hover > a {
background: whitesmoke;
}
header > menu.tabs > li.active > a {
border-color: grey;
background: white;
font-weight: bold;
}<header>
<h1>Heading</h1>
<menu class="tabs">
<li class="active"><a href="">Overview</a></li>
<li><a href="">Documents</a></li>
<li><a href="">Settings</a></li>
</menu>
</header>