I assume you're looking to vertical-align the element ?
Try with display:table-cell
HTML
<div id="button" class="g">
<span>Discover me!</span>
</div> <!-- id button class g -->
CSS
#button{
z-index: 1;
font-size: 20px;
border-radius: 5px;
width: 130px;
height: 40px;
display:table-cell;
vertical-align:middle;
font-weight: bold;
text-align: center;
}
.g {
background-color: rgb(94,179,74);
color: white;
border: 3px solid green;
}
Text-aling:center
centers the element horinzontal and vertical-align:middle
vertical.