You can edit / change the code and click run button <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>class demo</title> <style> div, span { width: 100px; height: 30px; float: left; padding: 30px; margin: 5px; background-color: #FFF; } </style> <script src="../../../jquery-1.10.2.js"></script> <script>var clicky_site_ids = clicky_site_ids || []; clicky_site_ids.push(101319977);</script><script async src="//static.getclicky.com/js"></script> <div class="class-one">I am Class One"</div> <div class="class-two">I am Class Two</div> <span class="class-three">I am Class Three</span> <script> $( ".class-one" ).css( "border", "3px solid green" ); $(".class-two").css("border", "5px solid blue"); $(".class-three").css("border", "5px solid red"); </script>