Untitled

dabblet.css

iframe {
	width:200px;
	height:200px;
	overflow:hidden;
	border:solid 1px #000;
	}
iframe:nth-child(2) {
	border-radius:50%;
	}
iframe:nth-child(3) {
	border-radius:10%;
	}
iframe:nth-child(4) {
	border-radius:40px;
	}

dabblet.html

<iframe src="data:text/html;charset=utf-8,<style>body{color:red}</style>Long line of red text"></iframe>
<iframe src="data:text/html;charset=utf-8,<style>body{color:red}</style>Long line of red text"></iframe>
<iframe src="data:text/html;charset=utf-8,<style>body{color:red}</style>Long line of red text"></iframe>
<iframe src="data:text/html;charset=utf-8,<style>body{color:red}</style>Long line of red text"></iframe>

settings.json

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