如何摆脱div之间的空间

Question

我的网页上有两条div之间有一条粗白线，每当我删除第二个div中的Main时，白线就会消失。如何删除白线并保留<ul>？我试过删除所有的CSS元素，但没有成功。即使空<ul>，空间就在那里......

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<ul>

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.header {
  width: 100%;
  height: 410px;
  background-color: #040104;
  text-align: center;
}
.nav {
  width: 100%;
  height: 50px;
  background-color: #040104;
  font-family: sans-serif;
  text-align: center;
}
.nav li {
  display: inline;
  color: #ce5e27;
  font-size: xx-large;
}
.nav ul li a {
  padding: 1em;
  color: #ce5e27;
  text-decoration: none;
}
.contentContainer {
  height: 600px;
  background-color: #040104;
}
.content {
  width: 60%;
  height: 200%;
  float: left;
  background-color: #040104;
  text-align: center;
}
.content h1 {
  font-family: sans-serif;
  font-size: x-large;
  color: #ce5e27;
}
.thumbnail {
  width: 40%;
  height: 200%;
  background-color: #040104;
  float: right;
  text-align: center;
}
.thumbnail h1 {
  font-family: sans-serif;
  font-size: large;
  color: #ce5e27;
}
.footer {
  clear: both;
  width: 100%;
  height: 60px;
  background-color: black;
  font-family: sans-serif;
  text-align: center;
}
.footer li {
  display: inline;
  color: #ce5e27;
  font-size: large;
}
.footer h1 {
  color: #ce5e27;
  font-size: small;
  text-align: center;
  font-family: sans-serif;
}

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Answer 1

您的<ul>自动带有保证金。将边距设置为0：

.nav ul{
    margin-top: 0px;
}

Answer 2

要摆脱白线，您可以将margin: 0添加到ul元素。

<强>演示：

.header {
  width: 100%;
  height: 410px;
  background-color: #040104;
  text-align: center;
}
ul {
  margin: 0;  
}
.nav {
  width: 100%;
  height: 50px;
  background-color: #040104;
  font-family: sans-serif;
  text-align: center;
}
.nav li {
  display: inline;
  color: #ce5e27;
  font-size: xx-large;
}
.nav ul li a {
  padding: 1em;
  color: #ce5e27;
  text-decoration: none;
}
.contentContainer {
  height: 600px;
  background-color: #040104;
}
.content {
  width: 60%;
  height: 200%;
  float: left;
  background-color: #040104;
  text-align: center;
}
.content h1 {
  font-family: sans-serif;
  font-size: x-large;
  color: #ce5e27;
}
.thumbnail {
  width: 40%;
  height: 200%;
  background-color: #040104;
  float: right;
  text-align: center;
}
.thumbnail h1 {
  font-family: sans-serif;
  font-size: large;
  color: #ce5e27;
}
.footer {
  clear: both;
  width: 100%;
  height: 60px;
  background-color: black;
  font-family: sans-serif;
  text-align: center;
}
.footer li {
  display: inline;
  color: #ce5e27;
  font-size: large;
}
.footer h1 {
  color: #ce5e27;
  font-size: small;
  text-align: center;
  font-family: sans-serif;
}

<div class="header">
  <img src="images/basketball-rims-header.gif">
</div>
<div class="nav">
  <ul>
    <li> <a href="index.html">Home</a>
    </li>
    <li>|</li>
    <li> <a href="http://www.nba.com/news/">News</a>
    </li>
    <li>|</li>
    <li> <a href="http://stats.nba.com/players/?ls=iref:nba:gnav">Players</a>
    </li>
    <li>|</li>
    <li> <a href="http://www.nba.com/teams/?ls=iref:nba:gnav">Teams</a>
    </li>
    <li>|</li>
  </ul>
</div>