html {
background-color: #9bf6ff;
font-family: 'Oswald', sans-serif;
width: auto;
}
#headerExperience {
line-height: 200px;
font-family: "proxima nova bold", "Helvetica Neue", Helvetica, Arial,
sans-serif;
color: khaki;
background-color: steelblue;
background-image: url("images/Experience background imagee.jpg") ;
background-size: cover;
background-position: center;
background-repeat: no-repeat;
text-align: center;
}<html>
<!--Header-->
<div id="headerExperience">
<h1>Experience</h1>
</div>
</html>experience
都是HTML元素的子元素。我试着用CSS格式化，但我在HTML背景和经验背景之间有差距。我尝试了很多方法，但都没有成功。如果您使用浏览器工具检查元素，您将看到在headerExperience元素上有一个21.4pxtop-margin。您可以添加reset到你的css重置所有margin和padding到0。然后，如果你想要边距和/或填充，你可以根据需要直接添加到你想要的元素。
*{
margin: 0;
padding: 0;
}
*{
margin: 0;
padding: 0;
box-sizing: border-box;
}
html {
background-color: #9bf6ff;
font-family: 'Oswald', sans-serif;
width: auto;
}
#headerExperience {
line-height: 200px;
font-family: "proxima nova bold", "Helvetica Neue", Helvetica, Arial, sans-serif;
color: khaki;
background-color: steelblue;
background-image: url("images/Experience background imagee.jpg");
background-size: cover;
background-position: center;
background-repeat: no-repeat;
text-align: center;
}<html>
<!--Header-->
<div id="headerExperience">
<h1>Experience</h1>
</div>
</html>