display
display: block; block element display
display: inline; inline element display
display: inline-block; block element display in line
display: flexbox; flexible box When the total width of the elements is less than the sum of the elements, the width is evenly distributed
display: none; hide
Positioning
position: static By default, there is no positioning,
position: fixed absolute positioning, relative to the browser. Common such as back to the top and the floating bar on both sides does not occupy space directly at the top, will block the bottom can not use top
position: elative relative positioning, relative normal position Use top to adjust from where it should be
position: absolute positioning, relative positioning of the parent element is not static
.aoa{
position:absolute;
border: red 1px solid;
background-color: blue;
top:40px;
display: none;
}
{.qaq
position: relative;
height: 40px;
line-height: 40px;
}
.qaq:hover .aoa{
display: block;
}
<ul>
<li class="qaq"> 十几万
<div class="aoa">
<ul>
<li>123</li>
<li>456</li>
</ul>
</div>
</li>
</ul>
Simple code to hide the drop-down menu bar