Non Standard Attribute
HTML
<h2>Non-standard attribute allowed:</h2>
<div jellyfish="blue" >Text</div>
<!-- Post Info -->
<div style='position:fixed;bottom:0;left:0;
background:lightgray;width:100%;'>
Use Data-* Instead: <a href='https://developer.mozilla.org/en-US/docs/Web/Guide/HTML/Using_data_attributes'>Data-* Attributes</a><br/>
<div>