Sometimes you want to apply styles with JavaScript. This can conflict with your responsive styles. For example: var list_items = document.querySelectorAll('.list__item'); var height = 0; var i; for(i = 0; i < list_items.length; i++) { height = Math.max(list_items[i].clientHeight, height); } for(i = 0; i < list_items.length; i++) { list_items[i].style.height = height + 'px'; } This script would run