Untitled

dabblet.css

div {width:350px; height:100px; background:lightgray; position:relative; margin:20px;}
div:after{content:''; width:160px; height:2px; background:gray; position:absolute; bottom:-2px; left: 100px}

dabblet.html

<div></div>

settings.json

{"view":"split","fontsize":"100","seethrough":"","prefixfree":"1","page":"css"}