Coding a dropdown menu

I'm working on a non-live template and i'm trying to add a custom code for a dropdown menu and when I change from my preview and refresh it the placement of my code has moved from the original spot to the center of my screen.
At times they will show up correctly with three duplicate menus in the center and others ! only have one in the correct place and all the others are centered on my page.

This is the code that I am placing on the custom css area

.dropbtn {
  background-color: #524f4f;
  color: white;
  padding: 16px;
  font-size: 25px;
  border: none;
  cursor: pointer;
}
.dropdown {
  position: relative;
  display: center;
}
.dropdown-content {
  display: none;
  position: absolute;
  background-color: #f1f1f1;
  min-width: 100%;
  box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
  z-index: 1;
}
.dropdown-content a {
  color: black;
  padding: 12px 16px;
  text-decoration: none;
  display: block;
}
.dropdown-content a:hover {background-color: #black;}
.dropdown:hover .dropdown-content {display: block;}
.dropdown:hover .dropbtn {background-color: #black;}

This is the code that I am using for the specific page

<center>
<div class="dropdown">
  <button class="dropbtn">rtu's</button>
  <div class="dropdown-content">
    <a href="#">allen bradley</a>
    <a href="#">idec</a>
    <a href="#">phoenix contact</a>
    <a href="#">roc</a>
    <a href+"#">totalflow</a>
  </div>
</div>
  </center>

Can you share link to your site?

Difficult to help with only code.

Need to see it for sure so we can help. 

I have a current site that is live on one template and i'm redoing it in a new template...

Is there a way that I can send you a link to my site without putting my changes live in the new template?

You can password the page in question or the whole site with a password, then post the link along with the password here. 

https://dahlia-accordion-jga7.squarespace.com/fab

bls123