CSS Nested List Affecting Parent Height - html

Question

In the below snippet I have a CSS menu using nested lists. A problem I have with it is that when you hover over the second list item, it reveals the nested list but in the process, increases the parent list's height pushing everything else down.
I'm aware I can use a position of absolute however that leads to a problem of the nested list not sitting below it's parent element and making it incredibly annoying to style for each nested list I may want.
Is there a simple way I can solve my problem while maintaining the nested loop sitting below it's parent (and by extension, making it possible to access with the :hover)
* {
margin: 0;
padding: 0;
}
nav ul {
list-style-type: none;
background: #000;
text-align: center;
}
nav ul li {
display: inline-block;
}
nav ul li a {
display: inline-block;
padding: 20px;
color: #fff;
text-decoration: none;
}
nav ul li a:hover {
background-color: #3ab795;
text-decoration: underline;
}
nav ul li > ul {
display: none;
position: relative;
left: 50px;
border: 1px solid #fff;
}
nav ul li > ul li {
display: block;
color: #fff;
}
nav ul li:hover > ul {
display: block;
}
<nav>
<ul>
<li>Item-1</li>
<li>Item-2
<ul>
<li>Item-2A</li>
<li>Item-2B</li>
<li>Item-2C</li>
<li>Item-2D</li>
</ul>
</li>
<li>Item-3</li>
<li>Item-4</li>
</ul>
</nav>

Answer 1

I hope your issue is fixed in below fiddle. Try it.
* {
margin: 0;
padding: 0;
}
nav ul {
list-style-type: none;
background: #000;
text-align: center;
}
nav ul li {
display: inline-block;
position: relative;
}
nav ul li a {
display: inline-block;
padding: 20px;
color: #fff;
text-decoration: none;
}
nav ul li a:hover {
background-color: #3ab795;
text-decoration: underline;
}
nav ul li > ul {
display: none;
position: absolute;
left: 50px;
top:100%;
border: 1px solid #fff;
}
nav ul li > ul li {
display: block;
color: #fff;
}
nav ul li:hover > ul {
display: block;
}
<nav>
<ul>
<li>Item-1</li>
<li>Item-2
<ul>
<li>Item-2A</li>
<li>Item-2B</li>
<li>Item-2C</li>
<li>Item-2D</li>
</ul>
</li>
<li>Item-3</li>
<li>Item-4</li>
</ul>
</nav>

Answer 2

For this you will need to understand the concept of position...Use position:absolute for the drop-menu and position:relative for its parent li...no need to write css for every drop-menu
* {
margin: 0;
padding: 0;
}
nav ul {
list-style-type: none;
background: #000;
text-align: center;
}
nav ul li {
display: inline-block;
position: relative;
}
nav ul li a {
display: inline-block;
padding: 20px;
color: #fff;
text-decoration: none;
}
nav ul li a:hover {
background-color: #3ab795;
text-decoration: underline;
}
nav ul li>ul {
display: none;
position: absolute;
top: 100%;
left: 0px;
border: 1px solid #fff;
min-width: 150px;
}
nav ul li>ul li {
display: block;
color: #fff;
}
nav ul li:hover>ul {
display: block;
}
<nav>
<ul>
<li>Item-1</li>
<li>Item-2
<ul>
<li>Item-2A</li>
<li>Item-2B</li>
<li>Item-2C</li>
<li>Item-2D</li>
</ul>
</li>
<li>Item-3
<ul>
<li>Item-3A</li>
<li>Item-3B</li>
<li>Item-3C</li>
<li>Item-3D</li>
</ul>
</li>
<li>Item-4</li>
</ul>
</nav>

Answer 3

There is nothing to worry about using absolute position for submenu. just make the parent relative. According to your code
nav ul li {
display: inline-block;
position: relative; // Added
}
and than modify nested ul like this
nav ul li > ul {
display: none;
position: absolute; // Added
left: 0; // Changed
border: 1px solid #fff;
width: 160px; // Change as per your requirement
}