HTML
<div class="btn" >
<span>X<span>
<div class="vertical_line"></div>
</div>
CSS
div.btn{
width:100px;
height:100px;
float:left;
border:1px solid #000000;
font-family:Arial, Helvetica, sans-serif;
font-size:80px;
text-align:center;
position: relative;
}
div.vertical_line{
width:0;
height:100px;
border:1px solid #000000;
position:absolute;
right:50px;
z-index:100;
margin:0;
padding:0;
}
div.btn span{
position:absolute;
z-index:0;
}
If you want to know how to center the 'X' in such a way that it overlaps with the vertical line, check out this jsfiddle.