Place button on bottom of div or screen
just do the button position:absolute without putting the div relativ
.button {
position: absolute;
bottom: 10px;
left: 50%;
margin-left: -104.5px; /*104.5px is half of the button's width*/
}
.test{
height:1000px;
}<div class="test">
<div>
<div>
<button class="button">
test
</button>
</div>
</div>
</div>if width div 50% then left must 25% if width div 70% then left must 15%
.center{
position:fixed;
bottom:20px;
left:20%;
width:60%;
}
.center .btn{
background:red;
width:100%;
color:white;
font-weight:bold;
border-radius: 64px;
padding:10px;
}<div class="center">
<button class="btn">Login</button>
</div>