If you're using Safari, some features may not work properly without vendor prefixes. For example, take a look at sticky headers:
Sticky headers
#sticky {
position: sticky;
position: -webkit-sticky;
top: 0;
background-color:cyan;
}
<div id="sticky">This is a sticky div.</div>
<p>This is some content...</p>
In addition, Safari lacks support for the details and summary elements. In such cases, it's best to use JavaScript.
for(var coll=document.getElementsByClassName("openbutton"),i=0;i<coll.length;i++)coll[i].addEventListener("click",function(){this.classList.toggle("active");var l=this.nextElementSibling;"block"===l.style.display?l.style.display="none":l.style.display="block"});
#menu {
display: none;
}
.list {
list-style: none;
}
<button class="openbutton">Open/Close</button>
<div class="menu">
<ul class="list">
<li>Option 1</li>
<li>Option 2</li>
<li>Option 3</li>
</ul>
</div>