A CodePen by Jeff Bail.

index.html

<p><strong>Example 1</strong>: The link below will be jumpy when hovered because borders take up space and there are none defined for the "off" state.</p>

<p><a href="#" class="border-jumpy">I'm jumpy</a></p>

<p><strong>Example 2</strong>: The link below has a transparent border in the "off" state, so it won't be jumpy when hovered.</p>

<p><a href="#" class="border-calm">I'm calm</a></p>

style.css

a {
 display:inline-block;
 padding:3px 12px;
}

.border-jumpy:hover {
 border:5px dotted gray; 
}

.border-calm {
 border:5px solid transparent; 
}
.border-calm:hover {
 border:5px dotted gray; 
}