My code only works on sololearn but not atom

ul{ list-style-type: none; margin:0; padding:0; width:250px; background-color: #f1f1f1; } li a{ display: block; padding:10px 12px; color:black; text-decoration:none; } li a:hover{ background-color:#555; color:white; } a.active{ background-color: lime; color:black; }

I was inspired

I found my mistake ady. Thank you!