Align button at the bottom of div using CSS

You can use position:absolute; to absolutely position an element within a parent div. When using position:absolute; the element will be positioned absolutely from the first positioned parent div, if it can't find one it will position absolutely from the window so you will need to make sure the content div is positioned.

To make the content div positioned, all position values that aren't static will work, but relative is the easiest since it doesn't change the divs positioning by itself.

So add position:relative; to the content div, remove the float from the button and add the following css to the button:

position: absolute;
right:    0;
bottom:   0;

Parent container has to have this:

position: relative;

Button itself has to have this:

position: relative;
bottom: 20px;
right: 20px;

or whatever you like

I have solved this using position fixed:

.button-corner {
  position: fixed;
  bottom: 20px;
  right: 20px;
}

CSS3 flexbox can also be used to align button at the bottom of parent element.

Required HTML:

<div class="container">
  <div class="btn-holder">
    <button type="button">Click</button>
  </div>
</div>

Necessary CSS:

.container {
  justify-content: space-between;
  flex-direction: column;
  height: 100vh;
  display: flex;
}
.container .btn-holder {
  justify-content: flex-end;
  display: flex;
}

Screenshot:

Useful Resources:

• Specs
• MDN
• CSS Tricks

* {box-sizing: border-box;}
body {
  background: linear-gradient(orange, yellow);
  font: 14px/18px Arial, sans-serif;
  margin: 0;
}
.container {
  justify-content: space-between;
  flex-direction: column;
  height: 100vh;
  display: flex;
  padding: 10px;
}
.container .btn-holder {
  justify-content: flex-end;
  display: flex;
}
.container .btn-holder button {
  padding: 10px 25px;
  background: blue;
  font-size: 16px;
  border: none;
  color: #fff;
}

<div class="container">
  <p>Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... Lorem ip sum dolor sit amet... </p>
  <div class="btn-holder">
    <button type="button">Click</button>
  </div>
</div>