JSFiddle - React, Tailwind, and code Playground

HTML

<a href="#" class="registrieren">Registrieren</a> 

<br><br><br>

    <button>
    Registrieren
</button>

CSS

.registrieren::before {
    content: url(http://fs1.directupload.net/images/150221/4wlu6kbs.png);;
}

.registrieren {
	font-size: 0.9em;
	text-decoration: none;
	color:hsl(20,50%,40%);
    padding:0.5em 0.5em 0.5em 0.8em;
    background-color:white;
    background-image: linear-gradient(hsl(0,0%,95%), hsl(0,0%,90%));
    border-radius:0.5em;
    border: 1px solid hsl(0,0%,88%);
    text-shadow: white 1px 1px;
	width: 7em;
	display: block;
}

.registrieren::before {
    content: url(http://fs1.directupload.net/images/150221/4wlu6kbs.png);
	vertical-align: sub;
	margin-right: 8px;
}




button {
  color:hsl(20,50%,40%);
    padding:0.5em;
    background-color:white;
    background-image: linear-gradient(hsl(0,0%,95%), hsl(0,0%,90%));
    border-radius:0.5em;
    border: 1px solid hsl(0,0%,88%);
    text-shadow: white 1px 1px;
	width:9em;
}

button::before {
    content: url(http://fs1.directupload.net/images/150221/4wlu6kbs.png);
	vertical-align: sub;
	margin-right: 7px;
	margin-left:5px;
}