-webkit-box-sizing: border-box;

dabblet.css

p {
  background: #f00 url(http://edsonjunior.com/sslm/images/sprite-bg-mensagem.png) no-repeat left center;
  border-bottom: 1px solid rgba(0, 0, 0, 0.246094);
  border-radius: 0.5em;
  color: #fff;
  font: bold 13px Tahoma, sans-serif;
  height: 1.5em;
  line-height: 1.5em;
  padding: 0.5em 1em 0.5em 3em;
  text-shadow: 0 -1px 0 rgba(0, 0, 0, 0.5);
  /* Uncomment the line below to see what happens */
  /*-webkit-box-sizing: border-box;*/
}

dabblet.html

<p>Invalid password!</p>

settings.json

{"view":"separate","fontsize":"80","seethrough":"","prefixfree":"1","page":"all"}