Try using display:table on the outer div and table-cell on the inner div.
jsFiddle example (border added to see alignment)
#outer {
height:230px;
border:1px solid #999;
display:table;
width:100%;
}
.inner {
display:table-cell;
vertical-align:middle;
text-align:center;
}
#text {
background:#e9e9e9;
padding:10px;
resize: none;
font-size: 10px;
color: #000;
height: 100px;
width: 95%;
}