Position: fixed

dabblet.css

/**
 * Position: fixed
 */

.bar {
	position: fixed;
	left: 20px;
	top: 50px;
	width: 100px;
	background: blue;
	color: #fff;
}
.foo {
	height: 1000px
}

dabblet.html

more content...
<div class="foo">
	<div class="bar">
		content
	</div>
</div>

dabblet.js

// alert('Hello world!');

settings.json

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