box-sizing

dabblet.css

/**
 * box-sizing
 */
 
 .test1 {
 width: 500px;
 margin: 20px auto;
 box-sizing: border-box;
 border:10px solid red;
}
 .test2 {
 width: 500px;
 margin: 20px auto;
 box-sizing: border-box;
 padding: 50px;
 border: solid blue 10px;
}
 .test3 {
 width: 500px;
 margin: 20px auto;
 box-sizing: content-box;
 padding: 50px;
 border: solid blue 10px;
}

dabblet.html

<div class="test1">hello</div>
<div class="test2">hi</div>
<div class="test3">world</div>

dabblet.js

// alert('Hello world!');

settings.json

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