box with 1:1 ratio
source: http://www.mademyday.de/css-height-equals-width-with-pure-css.html
<div class='box'>
<div class='content'>Aspect ratio of 1:1</div>
</div>
We need two block elements to achieve the desired behaviour. No images, no Javascript.
CSS
.box{
position: relative;
width: 50%; /* desired width */
}
.box:before{
content: "";
display: block;
padding-top: 100%; /* initial ratio of 1:1*/
}