Here is a way to center content both vertically and horizontally in any situation, which is useful when you do not know the width or height or both:
CSS
#container {
display: table;
width: 300px; /* not required, just for example */
height: 400px; /* not required, just for example */
}
#update {
display: table-cell;
vertical-align: middle;
text-align: center;
}
HTML
JSFiddle
Note that the width and height values are just for demonstration here, you can change them to anything you want (or remove them entirely) and it will still work because the vertical centering here is a product of the way the table-cell
display property works.