在网页设计中，我们经常需要为页面设置一个背景图或背景色，并确保它能覆盖整个可视区域，甚至在内容超出屏幕高度时，也能随着滚动条的出现而持续延伸。然而，在某些布局下，尤其是当页面内容较长导致出现滚动条时，可能会发现页面底部出现一块不属于原设计背景的区域，通常是浏览器默认的白色背景或其他父元素的背景色，这极大地破坏了页面的整体视觉一致性。这种现象通常是由于css样式设置不当，导致背景或叠加层未能正确地覆盖整个可滚动内容区域所致。
导致背景未完全覆盖或出现意外背景区域的原因，通常与以下CSS属性的理解和使用有关：
在原始代码中，body设置了height: 100%，并且.overlayE使用了position: absolute; height: 100% !important;。当页面内容超出视口高度时，body的背景没有随之延伸，同时overlayE作为absolute定位的元素，也无法固定在视口中并覆盖所有滚动内容，从而导致了底部出现非预期的背景。
要解决上述问题，并确保页面背景及叠加层能够完美覆盖整个可滚动区域，我们可以通过调整body和叠加层的CSS属性来实现。
为了避免在计算元素尺寸时出现意外的边距和内边距问题，建议在项目开始时就统一使用box-sizing: border-box;。这会使得元素的width和height包含其padding和border，简化布局计算。
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*,
*::before,
*::after {
margin: 0;
padding: 0;
box-sizing: border-box; /* 统一盒模型 */
}为了让body的背景能够覆盖整个可滚动区域，即使内容超出视口高度，我们不需要对body设置固定的height: 100%，而是让它自然地根据内容撑开。关键在于控制body的滚动行为。
将body的overflow-y属性设置为scroll。这会明确告诉浏览器，当内容超出body高度时，在Y轴方向上显示滚动条，并且body的背景会随着内容的延伸而向下铺满。
body {
font-family: Open Sans, "Helvetica Neue", "Helvetica", Helvetica, Arial, sans-serif;
font-size: 13px;
background-color: #000000 !important;
background-size: cover;
margin: 0;
/* height: 100%; */ /* 移除或注释掉此行，让body高度由内容决定 */
overflow-y: scroll; /* 确保body可滚动，且背景延伸 */
background-image: url("https://media.istockphoto.com/photos/programming-source-code-on-digital-screen-software-developer-and-picture-id1336271758?b=1&k=20&m=1336271758&s=170667a&w=0&h=HoJqtqo1r54eZf9G4OqBXRHXLsYoD0X9wMR-vXFBiTE=");
}对于像.overlayE这样的背景叠加层，如果希望它始终覆盖整个浏览器视口，无论页面如何滚动，就应该使用position: fixed。
.overlayE {
position: fixed; /* 从absolute改为fixed，使其相对于视口固定 */
width: 100%;
height: 100% !important;
margin: 0;
padding: 0;
z-index: -1;
background-color: rgba(0, 0, 0, 0.886);
}通过将.overlayE的position设置为fixed，它会相对于浏览器视口定位，并始终占据100%的宽度和高度，从而实现完美的覆盖效果。
以下是整合了上述修改后的CSS和HTML代码片段：
HTML结构 (experience.html)
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Work Experience</title>
<link rel="stylesheet" href="experience.css">
<script src="experience.js"></script>
<link href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,700,900&" rel="stylesheet" />
<link href="https://fonts.googleapis.com/css?family=Open+Sans:400,700&subset=latin,latin-ext" rel="stylesheet" />
<link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/4.4.0/css/font-awesome.min.css" rel="stylesheet" />
<link href="https://cdnjs.cloudflare.com/ajax/libs/animate.css/3.2.6/animate.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/wow/1.1.2/wow.min.js"></script>
</head>
<body>
<div class="overlayE"></div>
<div id="workexperience">
<div class="row ">
<div class="sectiontitle">
<h2>Work experience</h2>
<span class="headerLine"></span>
</div>
<ul class="cbp_tmtimeline">
<li>
<div class="cbp_tmicon cbp_tmicon-phone">
<i class="faPra fa-briefcase"></i>
</div>
<div class="cbp_tmlabel wow fadeInRight animated">
<h3>Web developer</h3>
<div class="date">
<i class="fa fa-calendar"></i>April 2014 - Current
</div>
<h4><i class="fa fa-flag"></i>Davic Company, Bratislava</h4>
<p class="projectParagraph">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Fugit obcaecati ipsa quae, iusto laudantium qui, nisi eum modi perspiciatis quasi facilis corporis iure soluta enim incidunt itaque aspernatur sequi tempora.</p>
</div>
</li>
<li>
<div class="cbp_tmicon cbp_tmicon-screen">
<i class="faPra fa-briefcase"></i>
</div>
<div class="cbp_tmlabel wow fadeInRight animated">
<h3>Web designer</h3>
<h4><i class="fa fa-flag"></i>Fannous Company, Prague</h4>
<div class="date"><i class="fa fa-calendar"></i>June 2012 - April 2014</div>
<p class="projectParagraph">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Deserunt quasi perspiciatis, aliquid sed maiores accusamus. Adipisci quidem nostrum quos quae doloremque esse a, ipsum earum, recusandae omnis dignissimos et sint.</p>
</div>
</li>
<li>
<div class="cbp_tmicon cbp_tmicon-mail">
<i class="faPra fa-briefcase"></i>
</div>
<div class="cbp_tmlabel wow fadeInRight animated">
<h3>Web designer</h3>
<h4><i class="fa fa-flag"></i>Techixs Company, London</h4>
<div class="date"><i class="fa fa-calendar"></i>November 2009 - June 2012</div>
<p class="projectParagraph">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nulla labore atque alias ipsa, nam quod rerum repellat cumque, aliquam sequi vitae voluptatibus cum soluta incidunt tempore accusamus eius sed excepturi!Lorem ipsum dolor sit amet,
consectetur adipisicing elit. Tempora natus veritatis aperiam repellendus dolor vel, expedita assumenda eos, mollitia quae ullam esse voluptas vero. Dolores culpa eaque vitae eum quibusdam?</p>
</div>
</li>
<li>
<div class="cbp_tmicon cbp_tmicon-phone">
<i class="faPra fa-briefcase"></i>
</div>
<div class="cbp_tmlabel wow fadeInRight animated">
<h3>Freelancer</h3>
<div class="date"><i class="fa fa-calendar"></i>Januar 2006 - November 2009</div>
<p class="projectParagraph">Lorem ipsum dolor sit amet, consectetur adipisicing elit. Esse iusto, possimus hic at quisquam, incidunt illo asperiores et nobis, qui nulla consequatur molestiae quibusdam expedita dignissimos? Iste eum velit quos.</p>
</div>
</li>
</ul>
</div>
</div>
</body>
</html>CSS样式 (experience.css)
*,
*::before,
*::after {
margin: 0;
padding: 0;
box-sizing: border-box; /* 统一盒模型 */
}
body {
font-family: Open Sans, "Helvetica Neue", "Helvetica", Helvetica, Arial, sans-serif;
font-size: 13px;
background-color: #000000 !important;
background-size: cover;
margin: 0;
/* 原始代码中的 height: 100%; 可能会导致问题，在此处移除或不设置 */
overflow-y: scroll; /* 关键：确保body可滚动，且背景延伸 */
background-image: url("https://media.istockphoto.com/photos/programming-source-code-on-digital-screen-software-developer-and-picture-id1336271758?b=1&k=20&m=1336271758&s=170667a&w=0&h=HoJqtqo1r54eZf9G4OqBXRHXLsYoD0X9wMR-vXFBiTE=");
}
.overlayE {
position: fixed; /* 关键：从absolute改为fixed，使其相对于视口固定 */
width: 100%;
height: 100% !important;
margin: 0;
padding: 0;
z-index: -1;
background-color: rgba(0, 0, 0, 0.886);
}
/* 以下为原始CSS中其他不变的样式，为保持完整性保留 */
body,
div,
dl,
dt,
dd,
ul,
ol,
li,
h1,
h2,
h3,
h4,
h5,
h6,
pre,
form,
p,
blockquote,
th,
td {
margin: 0;
padding: 0;
font-size: 13px;
direction: ltr;
}
.sectionClass1 {
padding: 80px 0px 50px 0px;
position: relative;
display: block;
}
.row {
width: 980px;
height: 100%;
max-width: 100%;
margin: 0 auto;
}
.row:before,
.row:after {
content: "";
display: table;
}
.sectiontitle {
background-position: center;
text-align: center;
min-height: 20px;
}
.sectiontitle h2 {
font-size: 30px;
color: #222;
margin-bottom: 0px;
padding-right: 10px;
padding-left: 10px;
}
.headerLine {
width: 160px;
height: 2px;
display: inline-block;
background: #101F2E;
}
.fullWidth {
width: 100%;
display: table;
float: none;
padding: 0;
min-height: 1px;
height: 100%;
position: relative;
}
/********************************/
/* SECTION WORK EXPERIENCE
********************************/
#work-experience .sectiontitle .headerLine {
width: 280px;
}
#work-experience .headerline {
width: 280px;
}
.cbp_tmtimeline {
margin: 60px 30px 0 0;
padding: 0;
list-style: none;
position: relative;
}
.cbp_tmtimeline:before {
content: '';
position: absolute;
top: 3%;
bottom: 0;
width: 10px;
background: #324454;
left: 13%;
height: 100%;
}
.cbp_tmtimeline li:last-child:before {
content: initial;
}
.cbp_tmtimeline>li .cbp_tmtime {
display: block;
width: 25%;
padding-right: 100px;
position: absolute;
}
.cbp_tmtimeline>li .cbp_tmtime span {
display: block;
text-align: right;
}
.cbp_tmtimeline>li .cbp_tmtime span:first-child {
font-size: 0.9em;
color: #bdd0db;
}
.cbp_tmtimeline>li .cbp_tmtime span:last-child {
font-size: 2.9em;
color: #3594cb;
}
.cbp_tmtimeline>li:nth-child(odd) .cbp_tmtime span:last-child {
color: #6cbfee;
}
.cbp_tmtimeline>li .cbp_tmlabel {
margin: 0 0 15px 25%;
background: rgba(50, 68, 84, 1);
color: #FFF;
padding: 30px;
font-size: 1.2em;
font-weight: 300;
line-height: 1.4;
font-family: 'Open Sans';
position: relative;
border-radius: 5px;
min-height: 150px;
}
.cbp_tmtimeline>li:nth-child(odd) .cbp_tmlabel {
background: #2B3A48;
}
.cbp_tmtimeline>li .cbp_tmlabel h3 {
margin-top: 0px;
color: white;
font-size: 20px;
margin-bottom: 5px;
padding: 0 0 10px 0;
border-bottom: 1px solid rgba(255, 255, 255, 0.4);
font-family: 'Open Sans', sans-serif;
font-weight: bold;
}
.cbp_tmtimeline>li .cbp_tmlabel h4 {
opacity: 0.7;
color: rgba(255, 255, 255, 1);
letter-spacing: 0px;
font-family: 'Source Sans Pro', sans-serif;
font-size: 18px;
line-height: 1.2em;
font-weight: 600;
padding: 0;
padding-bottom: 10px;
margin: 0;
text-align: left;
}
.cbp_tmtimeline>li .cbp_tmlabel h4 i {
margin-right: 5px;
vertical-align: middle;
}
.cbp_tmtimeline>li .cbp_tmlabel:after {
right: 100%;
border: solid transparent;
content: " ";
height: 0;以上就是HTML/CSS页面背景全覆盖与叠加层固定技巧的详细内容，更多请关注php中文网其它相关文章！
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