<style>
.hr {
  color: gray;
  border-style: inset;
  border-width: 1px;
  margin: 0.5em auto;
}
</style>
<div class=hr></div>
<div class=hr style="width: 50%"></div>
<div class=hr style="width: 100px"></div>
<div class=hr style="width: 100px"></div>
<div class=hr style="width: 100px"></div>
<div class=hr style="width: 100.99px"></div>
<div class=hr style="width: 0%"></div>
<div class=hr style="width: 0%"></div>
<div class=hr style="width: 0%"></div>
<div class=hr style="width: 0%"></div>
<div class=hr></div>